sentinel

 
Pronunciation: /ˈsɛntɪn(ə)l/

noun

  • 1a soldier or guard whose job is to stand and keep watch: soldiers stood sentinel with their muskets
  • 2 Medicine an indicator of the presence of disease: [as modifier]: the first national HIV sentinel surveillance programme in the developing world

verb (sentinels, sentinelling, sentinelled; US sentinels, sentineling, sentineled)

[with object]
  • station a soldier or guard by (a place) to keep watch: a wide course had been roped off and sentinelled with police

Origin:

late 16th century: from French sentinelle, from Italian sentinella, of unknown origin