D defs.my
Entry 4 senses Webster, 1913

Lookout

/lo͝ok'-outˌ/ · Look·out · IPA /ˈlʊkaʊt/
01 n. A careful looking or watching for any object or event.
  1. 1.
    A careful looking or watching for any object or event.
  2. 2.
    The place from which such observation is made.
  3. 3.
    A person engaged in watching; a sentinel; a sentry.
  4. 4.
    Object or duty of forethought and care; responsibility.[Colloq.]
Phrases & compounds
on the lookout for — in search of; looking for.