1. 不断供给
If you ply someone with food or drink, you keep giving them more of it.

2. 不断问；追问
If you ply someone with questions, you keep asking them questions.

3. 从事，经营（尤指街头销售或服务）
If you ply a trade, you do a particular kind of work regularly as your job, especially a kind of work that involves trying to sell goods or services to people outdoors.

4. （船、飞机或车辆）定期往返于
If a ship, aircraft, or vehicle plies a route, it makes regular journeys along that route.

1. (usually in combinations) one of several layers of cloth or paper or wood as in plywood

2. one of the strands twisted together to make yarn or rope or thread
often used in combination

e.g. three-ply cord
four-ply yarn