sentinel
1. sen.ti.nel \'sent-n*l, -*n-*l\ n [MF sentinelle, fr. OIt sentinella, fr. sentina vigilance, fr]. sentire to perceive, fr. L : one that watches or guards : SENTRY 2. sentinel vt or sen.ti.neled or sen.ti.nelled; or sen.ti.nel.ing; or sen.ti.nel.ling 1: to watch over as a sentinel 2: to furnish with a sentinel 3: to post as sentinel