tap

from The American Heritage® Dictionary of the English Language, 5th Edition.

• intransitive verb To strike gently with a light blow or blows.
• intransitive verb To give a light rap with.
• intransitive verb To produce with a succession of light blows.
• intransitive verb To select, as for membership in an organization; designate. synonym: appoint.
• intransitive verb To repair (shoe heels or toes) by applying a thin layer of leather or a substitute material.
• intransitive verb To attach metal plates to (shoe toes or heels).
• intransitive verb To deliver a gentle, light blow or blows.
• intransitive verb To walk making light clicks.
• noun A gentle blow.
• noun The sound made by such a blow.
• noun A thin layer of leather or a substitute applied to a worn-down shoe heel or toe.
• noun A metal plate attached to the toe or heel of a shoe, as for tap-dancing.
• noun A valve and spout used to regulate delivery of a fluid at the end of a pipe.
• noun A plug for a bunghole; a spigot.
• noun Liquor drawn from a spigot.
• noun Liquor of a particular brew, cask, or quality.
• noun Medicine The removal of fluid from a body cavity.
• noun A tool for cutting an internal screw thread.
• noun A makeshift terminal in an electric circuit.
• noun A wiretap.
• transitive verb To furnish with a spigot or tap.
• transitive verb To pierce in order to draw off liquid.
• transitive verb To draw (liquid) from a vessel or container.
• transitive verb Medicine To withdraw fluid from (a body cavity).
• transitive verb To make a physical connection with or open outlets from.
• transitive verb To wiretap (a telephone or communications channel).
• transitive verb To establish an electric connection in (a power line), as to divert current secretly.
• transitive verb To establish access to or a connection with.
• transitive verb To take advantage of; make use of.
• transitive verb To cut screw threads in (a collar, socket, or other fitting).
• transitive verb Informal To ask (a person) for money.
• idiom (on tap) Ready to be drawn; in a tapped cask.
• idiom (on tap) Available for immediate use; ready.

from The Century Dictionary.

• noun A tanners' pit, usually sunk below the surface of the tan-yard, in which bark is extracted with water and the process of tanning is carried out. Also called leach or latch.
• noun The hole bored and threaded in a street-main of a water-works system, so that the service-pipe of the customer may be connected thereto.
• noun In electricity, a branch line which taps the main circuit so as to divert a portion of the current; a shunt.
• To cut an internal screw-thread in with a screw-cutting tool, hob, or tap: as, to tap a nut or a hole.
• In electricity, to divert a portion of (the current) from a circuit by means of a branch circuit or shunt; to make electrical connection with (a circuit) at any point.
• noun A gentle blow; a slight blow, as with the fingers or a small thing.
• noun pl. Milit., a signal on a drum or trumpet, sounded about a quarter of an hour after tattoo, at which all lights in the soldiers' quarters must be extinguished.
• noun A piece of leather fastened upon the bottom of a boot or shoe in repairing or renewing the sole or heel.
• noun A tap-house or tap-room; also, the room in a tavern where liquor is drawn and served to guests.