Source : Webster's Revised Unabridged Dictionary (1913)

Bastardly \Bas"tard*ly\, a.
   Bastardlike; baseborn; spurious; corrupt. [Obs.] -- adv. In
   the manner of a bastard; spuriously. [Obs.] --Shak. Donne.

Source : WordNet®

bastardly
     adj : born out of wedlock; "the dominions of both rulers passed
           away to their spurious or doubtful offspring"-
           E.A.Freeman [syn: {bastard}, {misbegot}, {misbegotten},
            {spurious}]