a thickness or layer of a folded or laminated material

tiles that have a black PVC ply in the lamination

(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

work steadily with (a tool)

a tailor delicately plying his needle

(of a vessel or vehicle) travel regularly over a route, typically for commercial purposes

ferries ply across a strait to the island

provide someone with (food or drink) in a continuous or insistent way

she plied me with tea and scones