to not notice something, or not see how important it is [= miss]:
It is easy to overlook a small detail like that.
Nobody could overlook the fact that box office sales were down.
to forgive someone's mistake, bad behaviour etc and take no action:
She found him entertaining enough to overlook his faults.
if a house, room etc overlooks something, it has a view of it, usually from above:
Our room overlooks the ocean.