The Collaborative International Dictionary of English v.0.48:

Nihil \Ni"hil\, n. [L.]
   Nothing.
   [1913 Webster]

   Nihil album [L., white nothing] (Chem.), oxide of zinc. See
      under Zinc.

   Nihil debet [L., he owes nothing] (Law), the general issue
      in certain actions of debt.

   Nihil dicit [L., he says nothing] (Law), a declinature by
      the defendant to plead or answer. --Tomlins.
      [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

NIHIL DICIT. He says nothing. It is the failing of the defendant to put in a
plea or answer to the plaintiff's declaration by the day assigned; and in
this case judgment is given against the defendant of course, as he says
nothing why it should not. Vide 15 Vin. Ab. 556; Dane's Ab. Index, h.t.