The Collaborative International Dictionary of English v.0.48:

Dolus \Do"lus\, n. [L., deceit; akin to Gr. ?.] (Law)
   Evil intent, embracing both malice and fraud. See Culpa.
   --Wharton.
   [1913 Webster]

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

DOLUS, civil law. A fraudulent address or trick used to deceive some one; a
fraud. Dig. 4, 3, 1; Code, 2, 21.
     2. Dolus differs from fault in this, that the latter proceeds from an
error of the understanding; while to constitute the former there must be a
will or intention to do wrong. Wolff, Inst. Sec. 17.