on tap Definition

tap²
noun

1. A device consisting of a valve, with a handle for opening and shutting it, attached to a pipe for controlling the flow of liquid or gas.

Thesaurus: faucet (US), spigot (US), valve, spout.
2. A peg or stopper, especially in a barrel.
3. A receiver for listening to and recording private conversations, attached secretly to a telephone wire.
4. An act of attaching such a receiver to a telephone wire.
5. especially medicine.
The withdrawal of fluid from a place, especially (medicine) from a cavity in the body.
Example: spinal tap
6. A screw for cutting an internal thread.

verb tapped, tapping

1. To get liquid from (a barrel or a cavity in the body, etc) by piercing it or opening it with, or as if with, a tap.
2. To let out (liquid) from a vessel by opening, or as if by opening, a tap.
3. To get sap from (a tree) by cutting into it.
4. To attach a receiver secretly to (a telephone wire) so as to be able to hear private conversations.
5. To start using (a source, supply, etc).

Thesaurus: draw upon, make use of, use, consume, realize, take advantage of.
6. colloq
To ask or obtain (money) from them.
Form: tap someone for something (usually)

Idiom: on tap

Said of beer: stored in casks from which it is served.

Ready and available for immediate use.

Etymology: Anglo-Saxon tæppa.