a fluid or viscous substance used for writing or printing.

a dark, protective fluid ejected by the cuttlefish and other cephalopods.

Informal . publicity, esp. in print media

Their construction plans got some ink in the local paper.

to mark, stain, cover, or smear with ink

to ink one's clothes.

Slang . to sign one's name to (an official document)

We expect to ink the contract tomorrow.