to continuously watch a place or pay attention in order to find something you want or to be ready for problems or opportunities [↪ look out for]:
We're always on the lookout for new business opportunities.
Police were on the lookout for anyone behaving suspiciously.
to keep watching carefully for something or someone, especially for danger
keep a lookout for
We were instructed to keep a lookout for enemy aircraft.
When you're driving, keep a sharp lookout (=watch extra carefully) for cyclists.
someone whose duty is to watch carefully for something, especially for danger
a place for a lookout to watch from