A*lert" (*lrt"), a. [F. alerte, earlier à l'erte on the watch, fr. It. all' erta on the watch, prop. (standing) on a height, where one can look around; erta a declivity, steep, erto steep, p. p. of ergere, erigere, to erect, raise, L. erigere. See Erect.] 1. Watchful; vigilant; active in vigilance.