A pigment (or dye)-based fluid used for writing, printing etc.

(countable) A particular type, color or container of this fluid.

The black or dark-colored fluid ejected by squid, octopus etc, as a protective strategy.

(slang, uncountable) Publicity.

(slang, uncountable) Tattoo work.

(slang) Cheap red wine.

(transitive) To apply ink to; to cover or smear with ink.

(transitive) To sign (a contract or similar document).

(transitive) To apply a tattoo to (someone).

(intransitive, of a squid or octopus) to eject ink (sense 3)