Definitions from Wiktionary ( )

▸ adjective:  (usually not comparable) Physically unobstructed, uncovered, etc.
▸ adjective:  Able to have something pass through or along it.
▸ adjective:  Not covered, sealed, etc.; having an opening or aperture showing what is inside.
▸ adjective:  Not physically drawn together, folded or contracted.
▸ adjective:  Of a space, free of objects and obstructions.
▸ adjective:  (medicine) Resulting from an incision, puncture or any other process by which the skin no longer protects an internal part of the body.
▸ adjective:  (engineering, gas and liquid flow, of valve or damper) In a position allowing fluid to flow.
▸ adjective:  (of a sandwich, etc., usually not comparable) Composed of a single slice of bread with a topping.
▸ adjective:  (now regional) Not of a quality to prevent communication, as by closing waterways, blocking roads, etc.; hence, not frosty or inclement; mild; used of the weather or the climate.
▸ adjective:  Able to be used or interacted with in some way.
▸ adjective:  (not comparable) Available for use or operation.
▸ adjective:  (not comparable) Actively conducting or prepared to conduct business.
▸ adjective:  (not comparable) Allowing entrance to visitors or the public.
▸ adjective:  (comparable) Receptive.
▸ adjective:  (comparable, with 'to') Susceptible or vulnerable (to the stated means).
▸ adjective:  (computing, not comparable, of a file, document, etc.) In current use; connected to as a resource.
▸ adjective:  (computing, of a program or application, especially one with a screen-based interface) Running.
▸ adjective:  Not hidden or restricted.
▸ adjective:  Not concealed; overt.
▸ adjective:  Of a person, not concealing their feelings, opinions, etc.; candid, ingenuous.
▸ adjective:  (not comparable) Public.
▸ adjective:  (law, of correspondence) Written or sent with the intention that it may made public or referred to at any trial, rather than by way of confidential private negotiation for a settlement.
▸ adjective:  (not comparable) With open access, of open science, or both.
▸ adjective:  (computing, education) Made public, usable with a free licence and without proprietary components.
▸ adjective:  (sports) Of a tournament or competition, allowing anyone to enter, especially or originally irrespective of professional or amateur status.
▸ adjective:  (sports and games) Characterised by free-flowing play.
▸ adjective:  Not completed or finalised.
▸ adjective:  Not settled; not decided or determined; not withdrawn from consideration.
▸ adjective:  (sometimes business) Not fulfilled or resolved; incomplete.
▸ adjective:  Not having one end joined to the other; not forming a closed loop.
▸ adjective:  (electricity, of a switch or circuit breaker) In a position such that a circuit is not completed, preventing electricity from flowing.
▸ adjective:  (graph theory, of a walk) Having different first and last vertices.
▸ adjective:  (phonetics, of a syllable) Ending in a vowel; not having a coda.
▸ adjective:  (mathematics, logic, of a formula) Having a free variable.
▸ adjective:  (mathematics, topology, of a set) Which is part of a predefined collection of subsets of X, that defines a topological space on X.
▸ adjective:  (music, stringed instruments) Of a note, played without pressing the string against the fingerboard.
▸ adjective:  (music) Of a note, played without closing any finger-hole, key or valve.
▸ adjective:  (phonetics, sometimes with comparative opener) Uttered with a relatively wide opening of the articulating organs; said of vowels.
▸ adjective:  (phonetics) Uttered, as a consonant, with the oral passage simply narrowed without closure.
▸ adjective:  (computing, used before "code") Source code of a computer program that is not within the text of a macro being generated.
▸ adjective:  (of a multi-word compound) Having component words separated by spaces, as opposed to being joined together or hyphenated; for example, time slot as opposed to timeslot or time-slot.
▸ adjective:  (especially sports) Of a club, bat or other hitting implement, angled upwards and/or (for a right-hander) clockwise of straight.
▸ verb:  To make or become physically unobstructed, uncovered, etc.
▸ verb:  (transitive, intransitive) To make or become accessible or clear for passage by moving from a shut position.
▸ verb:  (transitive, intransitive) To make or become clear by removal of objects and obstructions, so as to allow passage, access, or visibility.
▸ verb:  (transitive, intransitive) To unseal or uncover, or become unsealed or uncovered.
▸ verb:  (transitive, intransitive) To spread; to expand into a wider or looser position.
▸ verb:  (transitive, nursing) To make (a bed) ready for a patient by folding back the bedcovers.
▸ verb:  (transitive, intransitive, poker) To reveal one's hand.
▸ verb:  (transitive, intransitive, engineering, gas and liquid flow, of valve or damper) To move to a position allowing fluid to flow.
▸ verb:  (especially sports, transitive, intransitive) To angle (a club, bat or other hitting implement) upwards and/or (for a right-hander) clockwise of straight.
▸ verb:  (transitive, intransitive) To cause or allow a gap to form or widen.
▸ verb:  (transitive, intransitive, electricity, of a switch, fuse or circuit breaker) To move to a position preventing electricity from flowing.
▸ verb:  To make or become available for use or interaction.
▸ verb:  (transitive, intransitive) To make or become operative or available.
▸ verb:  (transitive, intransitive) To make or become accessible to customers, clients or visitors.
▸ verb:  (transitive, intransitive) To make or become receptive or susceptible (to something).
▸ verb:  (computing, transitive, intransitive) To connect to a resource (a file, document, etc.) for viewing or editing.
▸ verb:  (Manglish, Philippines, Quebec) To turn on; to switch on.
▸ verb:  To start or begin.
▸ verb:  (transitive or intransitive) To start (an event or activity) as the first performer or actor.
▸ verb:  (intransitive, with 'for') To precede another as a performer at a concert or show.
▸ verb:  (intransitive) Of an event, activity etc., to start or get underway.
▸ verb:  (transitive) To bring up, broach.
▸ verb:  (transitive) To enter upon, begin.
▸ verb:  (computing, transitive, intransitive) To start running (a program or application, especially one with a screen-based interface).
▸ verb:  (intransitive, cricket) To begin a side's innings as one of the first two batsmen.
▸ verb:  (intransitive, poker) To bet before any other player has in a particular betting round in a game of poker.
▸ verb:  (obsolete) To disclose; to reveal; to interpret; to explain.
▸ noun:  (in the definite) Open or unobstructed space; an exposed location.
▸ noun:  (in the definite) Public knowledge or scrutiny; full view.
▸ noun:  (electronics) A defect in an electrical circuit preventing current from flowing.
▸ noun:  A sports event in which anybody can compete, especially or originally irrespective of amateur or professional status.
▸ noun:  The act of something being opened, such as an e-mail message.

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