o'clock

adverb

1. (modifying a numeral, one to twelve) In conjunction with a numeral, indicates the time within a twelve-hour period (midnight to noon or noon to midnight), specifically the time when the hour hand of a clock points precisely to the symbol or marking corresponding to the designated numeral.“(rare, nonstandard) What o'clock is it?”
2. In conjunction with a term representing an action or event that occurs daily, indicates the time that said action or event occurs, or first occurs.
3. (with a numeral, one to twelve) In conjunction with a numeral, indicates the direction, relative to the speaker or a vehicle, especially an aircraft, corresponding to the direction the hour hand is pointing at the time corresponding to the numeral, with twelve representing directly ahead and three being to the right.