To Tap

1. To furnish with taps.
2. To draw off liquid from a vessel.
3. To deplete, especially of a liquid via a tap; to tap out.
4. To exploit.
5. To place a listening or recording device on a telephone or wired connection. [from 19th c.]
6. To intercept a communication without authority. Synonym: eavesdrop
7. (mechanical) To cut an internal screw thread.
8. (card games, board games) To turn or flip a card or playing piece to remind players that it has already been used that turn (by analogy to "tapping," in the sense of drawing on to the point of temporary exhaustion, the resources or abilities represented by the card).
9. (informal) To cadge, borrow or beg.
10. (medicine, informal) To drain off fluid by paracentesis.
11. To advance someone for a post or job, or for membership of a club