I.a looking out, watch, guard, as a duty, Hdt., Aesch.; φρουρὰν ἄζηλον ὀχήσω shall keep unenviable watch, Aesch.; φρουρὰ ὄμματος my watchful eye, Soph.; φρουρᾶς ᾁδειν to sing while on guard, Ar.
2.a prison, Plat.
II.of persons, a watch, guard, garrison, Hdt., Aesch., etc.; esp. of frontier-posts, which were guarded in Attica by the περίπολοι, Xen.