1. A black or colored liquid used for writing, drawing, or printing on paper or other writing surface.
2. A black liquid produced by some sea animals; such as, the octopus, cuttlefish, and squid in order to distract predators.

From an organ, found in most cephalopods, containing an inky fluid which can be ejected from a duct opening at the base of the siphon.

The purpose of the ink-fluid is to cloud the water and it provides and opportunity for these animals to escape from their enemies.

3. Etymology: from Old French enque, "dark writing fluid"; from Late Latin (about 300 to about700 A.D.) encaustum, which came from Greek enkauston, "purple" or "red ink"; used by the Roman emperors to sign documents, originally a form of enkaustos, "burned in".

The term enkaustos came from the stem of enkaiein, "to burn in"; from en, "in" + kaiein, "to burn"; based on Latin causticus, "burning, caustic"; from Greek kaustikos, "capable of burning" and from kaustos, "combustible"; from kaiein, the Greek element meaning "to burn".