Definition of "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: use diligently

"Ply your wits!."

verb: give what is desired or needed, especially support, food or sustenance

verb: wield vigorously

"Ply an axe."

verb: join together as by twisting, weaving, or molding

"Ply fabric."

verb: travel a route regularly

"Ships ply the waters near the coast."

verb: apply oneself diligently

"Ply one's trade."