The Collaborative International Dictionary of English v.0.48:

Scienter \Sci*en"ter\, adv. [L.] (Law)
   Knowingly; willfully. --Bouvier.
   [1913 Webster]

WordNet (r) 3.0 (2006):

scienter
    adv 1: (law) deliberately or knowingly

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

SCIENTER, knowingly.
     2. A man may do many acts which are justifiable or not, as he is
ignorant or not ignorant of certain facts. He may pass a counterfeit coin,
when he is ignorant of its being counterfeit, and is guilty of no offence;
but if he knew the coin to be counterfeit, which is called the scienter, he
is guilty of passing counterfeit money. A man who keeps an animal which
injures some person, or his property, is answerable for damages, or in some
cases he may be indicted if he had a knowledge of such animal's propensity
to do injury. 3 Blackst. Comm. 154; 2 Stark. Ev. 178; 4 Campb. 198; 2 Str.
1264; 2 Esp. 482;  Bull. N. P. 77; Burr. 2092; 2 Lev. 172; Lord Raym. 110; 2
B. & A. 620; 2 C. M. & R. 496; 5 C. & P. 1; S. C. 24 E. C. L. R. 187; 1
Leigh, N. P. 552, 553; 7 C. & P. 755.
     4. In this respect the civil law agrees with our own. Domat, Lois Civ.
liv. 2, t. 8, s. 2. As to what evidence maybe given to prove guilty
knowledge, see Archb. Cr. Pl. 109. Vide Animal; Dog.