Definition of "ack" in English

noun

1. (military, now historical) The letter A as used in signalling and other types of communications.

2. (data communications) acknowledgment signal

verb

1. Alternative form of ACK.

interjection

1. (radio communications) acknowledged

interjection

1. Expressing distaste, alarm, or trepidation.

2. (4chan slang, offensive) Mocking a transgender person by imitating the sound of choking during a suicide by hanging, evoking the notion that transgender people frequently commit suicide.