The Collaborative International Dictionary of English v.0.48:

Behead \Be*head"\, v. t. [imp. & p. p. Beheaded; p. pr. & vb.
   n. Beheading.] [OE. bihefden, AS. behe['a]fdian; pref. be-
   + he['a]fod head. See Head.]
   To sever the head from; to take off the head of.
   [1913 Webster]

WordNet (r) 3.0 (2006):

behead
    v 1: cut the head of; "the French King was beheaded during the
         Revolution" [syn: decapitate, behead, decollate]

Easton's 1897 Bible Dictionary:

Behead
   a method of taking away life practised among the Egyptians (Gen.
   40:17-19). There are instances of this mode of punishment also
   among the Hebrews (2 Sam. 4:8; 20:21,22; 2 Kings 10:6-8). It is
   also mentioned in the New Testament (Matt. 14:8-12; Acts 12:2).