Decollatio
Defined in 3 dictionaries — Cyclopedic (1922), Ballentine's (1916), Black's (1910)
The Cyclopedic Law Dictionary
Walter A. Shumaker and George Foster Longsdorf; ed. James C. Cahill · 1922
Decollation; beheading.
Ballentine's Law Dictionary
James A. Ballentine · 1916
Decapitation.
Black's Law Dictionary
Henry Campbell Black, M.A. · 1910
In old English and Scotch law. Decollation; the punishment of beheading. Fleta, lib. 1, c. 21, § 6.