If someone is decapitated, their head is cut off. A worker was decapitated when a lift plummeted down the shaft on top of him + decapitation decapitations de·capi·ta·tion executions by decapitation. to cut off someone's head (decapitatus, from caput )
[ di-'ka-p&-"tAt, dE- ] (transitive verb.) circa 1611. Late Latin decapitatus, past participle of decapitare, from Latin de- + capit-, caput head; more at HEAD.