The Collaborative International Dictionary of English v.0.48:

Piratical \Pi*rat"ic*al\, a. [L. piraticus, Gr. ?: cf. F.
   piratique.]
   Of or pertaining to a pirate; acquired by, or practicing,
   piracy; as, a piratical undertaking. "Piratical printers."
   --Pope. -- Pi*rat"ic*al*ly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

piratically
    adv 1: in a piratical manner; "the piratically published edition
           of his book"

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

PIRATICALLY, pleadings. This is a technical word, essential to charge the
crime of piracy in an indictment, which cannot be supplied by another word,
or any circumlocution. Hawk. B. 1, c. 37, s. 15; 3 Inst. 112; 1 Chit. Cr.
Law, *244.