Learn how to say Beheaded correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word behead:
cut off the head of (someone), especially as a form of execution:
Mary was beheaded at Fotheringhay
(as noun beheading)
a beheading on Tower Hill
Old English behēafdian; from be- ‘off’ (expressing removal) + hēafod (see head)