n. (Zool.) The ounce. [ 1913 Webster ]

adv. [ OE. ones, anes, an adverbial form fr. one, on, an, one. See One-, -Wards. ] 1. For one time; by limitation to the number one; not twice nor any number of times more than one. [ 1913 Webster ]

Ye shall . . . go round about the city once. Josh. vi. 3. [ 1913 Webster ]

Trees that bear mast are fruitful but once in two years. Bacon. [ 1913 Webster ]

2. At some one period of time; -- used indefinitely. [ 1913 Webster ]

My soul had once some foolish fondness for thee. Addison. [ 1913 Webster ]

That court which we shall once govern. Bp. Hall. [ 1913 Webster ]

3. At any one time; -- often nearly equivalent to ever, if ever, or whenever; as, once kindled, it may not be quenched. [ 1913 Webster ]

Wilt thou not be made clean? When shall it once be? Jer. xiii. 27. [ 1913 Webster ]

To be once in doubt
Is once to be resolved. Shak. [ 1913 Webster ]

☞ Once is used as a noun when preceded by this or that; as, this once, that once. It is also sometimes used elliptically, like an adjective, for once-existing. “The once province of Britain.” J. N. Pomeroy. [ 1913 Webster ]

At once. (a) At the same point of time; immediately; without delay. “Stand not upon the order of your going, but go at once.” Shak. “I . . . withdrew at once and altogether.” Jeffrey. (b) At one and the same time; simultaneously; in one body; as, they all moved at once. --
Once and again, once and once more; repeatedly. “A dove sent forth once and again, to spy.” Milton. [ 1913 Webster ]

n. a swift cursory examination or inspection; as, I gave him the once-over.
Syn. -- look-over. [ WordNet 1.5 ]