Quick definitions from WordNet (ply)

▸ noun:  (usually in combinations) one of several layers of cloth or paper or wood as in plywood
▸ noun:  one of the strands twisted together to make yarn or rope or thread; often used in combination ("Three-ply cord")
▸ verb:  apply oneself diligently ("Ply one's trade")
▸ verb:  use diligently ("Ply your wits!")
▸ verb:  wield vigorously ("Ply an axe")
▸ verb:  travel a route regularly ("Ships ply the waters near the coast")
▸ verb:  provide what is desired or needed, especially support, food or sustenance
▸ name:  A surname (very rare: popularity rank in the U.S.: #54880)

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▸ Also see ply