Qui vive

·- The challenge of a French sentinel, or patrol;

— used like the English challenge: "Who comes there?".

Vive
·adj Lively; animated; forcible. II. Vive ·- Long live, that is, success to; as, vive le roi, long ...

Webster's Dictionary of the English Language
qui
qui, quae, quod (old forms: nom. quei; gen. quojus; dat. quoi, and in inscrr. QVOEI, QVOIEI, and QVE...

A New Latin Dictionary by Charlton T. Lewis Ph.D. and Charles Short, LL. D.
qui
quī (1) quae, quod, gen.cuius (old, quoius), dat.cui (old, quoi), abl.quō, quā (with cum, m. quīcum...

An Elementary Latin Dictionary