The Collaborative International Dictionary of English v.0.48:

Paraph \Par"aph\, n. [F. paraphe, parafe, contr. fr.
   paragraphe.]
   A flourish made with the pen at the end of a signature. In
   the Middle Ages, this formed a sort of rude safeguard against
   forgery. --Brande & C.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Paraph \Par"aph\, v. t. [imp. & p. p. Paraphed; p. pr. & vb.
   n. Paraphing.] [Cf. F. parapher, parafer.]
   To add a paraph to; to sign, esp. with the initials.
   [1913 Webster]

WordNet (r) 3.0 (2006):

paraph
    n 1: a flourish added after or under your signature (originally
         to protect against forgery)