qui vive

• POS: Noun Phrase

CIDE DICTIONARY

qui vive,  [F., fr. qui who + vive, pres. subj. of vivre to live.].

 The challenge of a French sentinel, or patrol; -- used like the English challenge: “Who comes there?”  [1913 Webster]

To be on the qui vive, to be on guard; to be watchful and alert, like a sentinel.

OXFORD DICTIONARY

qui vive, n.

Idiom

on the qui vive on the alert; watching for something to happen.

Etymology

F, = lit. '(long) live who?', i.e. on whose side are you?, as a sentry's challenge