\Sen"ti*nel\, n. [F. sentinelle (cf. It. sentinella);
probably originally, a litle path, the sentinel's beat,, and
a dim. of a word meaning, path; cf. F. sente path. L. semita;
and OF. sentine, sentele, senteret, diminutive words. Cf.
{Sentry}.]
1. One who watches or guards; specifically (Mil.), a soldier
   set to guard an army, camp, or other place, from surprise,
   to observe the approach of danger, and give notice of it;
   a sentry.
         The sentinels who paced the ramparts. --Macaulay.
2. Watch; guard. [Obs.] ``That princes do keep due
   sentinel.'' --Bacon.
3. (Zo["o]l.) A marine crab ({Podophthalmus vigil}) native of
   the Indian Ocean, remarkable for the great length of its
   eyestalks; -- called also {sentinel crab}.

\Sen"ti*nel\, v. t. [imp. & p. p. {Sentineled}or
{Sentinelled}; p. pr. & vb. n. {Sentineling} or
{Sentinelling}.]
1. To watch over like a sentinel. ``To sentinel enchanted
   land.'' [R.] --Sir W. Scott.
2. To furnish with a sentinel; to place under the guard of a
   sentinel or sentinels.