Definitions from Wiktionary ( )

▸ verb:  (transitive)
▸ verb:  To hit (someone or something) hard, especially with a flat implement or a stick; to thrash, to whack.
▸ verb:  (also figuratively) To drive or force (someone or something) by, or as if by, beating or hitting; to knock.
▸ verb:  To pack (people or things) closely together; to cram.
▸ verb:  (figuratively) To decisively defeat (someone) in a contest; to beat, to thrash.
▸ verb:  (obsolete) To crowd or pack (a place or thing) with people, objects, etc.
▸ verb:  (intransitive)
▸ verb:  To fall down hard with a thump.
▸ verb:  (obsolete) To be crammed or filled full.
▸ verb:  (obsolete, rare) Of people: to crowd or pack a place.
▸ noun:  An act of hitting hard, especially with a flat implement or a stick; a whack; also, a powerful stroke involved in such hitting; a blow, a strike.
▸ noun:  A dull or heavy slapping sound.

---

▸ Word origin

▸ Words similar to thwack
▸ Usage examples for thwack

▸ Idioms related to thwack
▸ Wikipedia articles (New!)
▸ Popular adjectives describing thwack
▸ Words that often appear near thwack
▸ Rhymes of thwack

▸ Invented words related to thwack