Source : Webster's Revised Unabridged Dictionary (1913)

Basely \Base"ly\, adv.
   1. In a base manner; with despicable meanness; dishonorably;
      shamefully.

   2. Illegitimately; in bastardy. [Archaic] --Knolles.

Source : WordNet®

basely
     adv : in a despicable, ignoble manner; "this new leader meanly
           threatens the deepest values of our society" [syn: {meanly},
            {scurvily}]