o'clock

Meaning

Adverb

• 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.
• 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.
• 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.

Origin

• Shortened form of of the clock.