Abbreviation of chain - a unit of measurement equal to 22 yards

(nautical) An imaginary line between two objects that can be used to chart a safe course in a difficult situation.

(UK, intransitive, informal) To study in detail; to familiarize oneself with all available information. / (UK, transitive, informal) To inform or teach with all relevant details; to brief.

(computing) The process of scanning the state of a keyboard to determine which keys are being pressed.