IPA: //bɪˈhɛd//
KK: /bɪˈhɛd/
To cut off someone's head.
The ancient punishment for treason was to behead the traitor.
Past: beheaded
Past Participle: beheaded
Behead → It is formed from "be-" (meaning to cause to be) and "head" (from Old English "heafod", meaning the upper part of the body). The word "behead" means to cause the head to be removed from the body.
Think of 'causing' something to happen ('be-') and 'removing the head' — that's what behead means.