(1):
(v. t.) To inspect narrowly; to examine and keep watch upon; to watch; to observe.
(2):
(v. t.) To catch sight of; to perceive with the eyes; to discover, as a distant object partly concealed, or not obvious to notice; to see at a glance; to discern unexpectedly; to spy; as, to espy land; to espy a man in a crowd.
(3):
(v. i.) To look or search narrowly; to look about; to watch; to take notice; to spy.
(4):
(n.) A spy; a scout.