knock out

verb

• To strike or bump (someone or something) out.

  "I accidentally knocked out the glass in my picture frame."

• To render unconscious, as by a blow to the head.

  "The boxer knocked out his opponent in the third round."

• To put to sleep.

  "The allergy pill knocked him out for a good three hours."

• To exhaust.

  "Running errands all day really knocked him out."

• To complete, especially in haste; knock off.

  "They knocked out the entire project in one night."

• To cause a mechanism to become non-functional by damaging or destroying it.

  "The antitank gun knocked out the enemy tank."

• To eliminate.
• To communicate (a message) by knocking.

  "The prisoner knocked out a message on the wall for the prisoner in the adjoining cell."

• To lose the scent of hounds in fox-hunting.
• (Oxford University slang) To leave college after hours—after half-past ten at night when the doors has been locked.