ACK
What does ACK mean?
ACK means: an onomatopoeia for the sound somebody makes during a hanging, and is often used to cut short sentences or quotes, indicating that the person was hanged before the end of the sentence.
Category: Mental Illness & Suicide
Related terms: 41%, An Hero, Rope, kys, TCD / Total Cissoid Death
Source: Brainworms Glossary entry compiled from 4chan /lgbt/ and adjacent community usage.