The Collaborative International Dictionary of English v.0.48:

Nape \Nape\ (n[=a]p), n. [Perh. akin to knap a knop.]
   The back part of the neck. --Spenser.
   [1913 Webster]

WordNet (r) 3.0 (2006):

nape
    n 1: the back side of the neck [syn: nape, scruff, nucha]