The ninth hour of the day, reckoned from sunrise according to the Roman method, or about three o'clock in the afternoon. Obsolete.

With addition of dayes (also day) or of the day. Obsolete.

The time of nine hours after midnight or midday, esp. as indicated by a clock, watch, etc. Frequently in nine o'clock (formerly †nine of the clock).

In specifying a time of day, with ellipsis of hour, as one o'clock, half past one, one twenty five, etc.

With omission of hours (of the day): three o'clock (also attributive), also simply three; half-past three; three fifteen, 3.15 = a quarter past three.

absol. spec. With ellipsis of hours (of the day: cf. twelve hours n. at compounds 2c); also twelve o'clock.

twelve o'clock in the day, midday (also attributive); a meal or refreshment taken at noon.

with omission of hours, as four o'clock.

see sense A. 2c; also denoting any position resembling that of the hands of a clock at six o'clock.

As a measure of time. A fourth part of an hour; a point of time marking the transition from one fifteen-minute period to the next, as denoted by a…

the time to kiss, frequently used as a jocular reply to children who ask the time.