ply¹ / plī/ • n. (pl. plies) 1. a thickness or layer of a folded or laminated material. ∎  [usu. in comb.] a strand of yarn or rope: [as adj.] four-ply yarn. ∎  the number of layers or strands of which something is made: the yarn can be any ply from two to eight. ∎  [usu. in comb.] a reinforcing layer of fabric in a tire: [as adj.] a six-ply whitewall tire. 2. short for plywood.3. (in game theory) the number of levels at which branching occurs in a tree of possible outcomes, typically corresponding to the number of moves ahead (in chess strictly half-moves ahead) considered by a computer program. ∎  a half-move (i.e., one player's move) in computer chess.ply² • v. (plies, plied) [tr.] 1. work with (a tool, esp. one requiring steady, rhythmic movements): a tailor delicately plying his needle. ∎  work steadily at (one's business or trade); conduct: he plied a profitable export trade.2. [intr.] (of a vessel or vehicle) travel regularly over a route, typically for commercial purposes: ferries ply across a strait to the island. ∎  [tr.] travel over (a route) in this way: the motion of the big tug as it plied the Jersey coastline.3. (ply someone with) provide someone with (food or drink) in a continuous or insistent way: a flight attendant who plied them with soft drinks. ∎  direct (numerous questions) at someone: the presiding judge plied him with a series of absurd questions.

ply1 (Sc.) plight, condition XV; fold, layer XVI (in earliest use Sc.); bend, turn, twist XVI (fig. from XVII). — (O)F. pli, f. plier, †pleier (
whence ply vb. bend, lit. and fig. XIV) :— L. plicāre; cf. FOLD2.

ply2 apply, employ XIV; work away at; solicit earnestly XVI; (naut.) XVI. Aphetic of APPLY.