[sen.ti.nel] n [MF sentinelle, fr. OIt sentinella, fr. sentina vigilance, fr. sentire to perceive, fr. L] (1579): sentry
[2]sentinel vt -neled or -nelled ; -nel.ing or -nel.ling (1593) 1: to watch over as a sentinel
2: to furnish with a sentinel
3: to post as sentinel