Onomastic

from WordNet (r) 3.0 (2006)

onomastic
    adj 1: of or related to onomastics; "he published a collection
           of his onomastic essays"

from The Collaborative International Dictionary of English v.0.48

Onomastic \On`o*mas"tic\, a. [Gr. ?, from ? to name, 'o`noma
   name.] (Law)
   Applied to a signature when the body of the instrument is in
   another's handwriting. --Burrill.
   [1913 Webster]