Wordnet 3.0
ADVERB (2)
1. 
 in an unnecessary manner; 
- Example: "they were unnecessarily rude"2. 
 without any necessity; 
- Example: "this marathon would exhaust him unnecessarily"
The Collaborative International Dictionary of English v.0.48:
Unnecessary \Un*nec"es*sa*ry\, a.
   Not necessary; not required under the circumstances; unless;
   needless; as, unnecessary labor, care, or rigor. --
   Un*nec"es*sa*ri*ly, adv. -- Un*nec"es*sa*ri*ness, n.
   [1913 Webster]
   [1913 Webster]
WordNet (r) 3.0 (2006):
unnecessarily
    adv 1: in an unnecessary manner; "they were unnecessarily rude"
           [ant: necessarily, needfully]
    2: without any necessity; "this marathon would exhaust him
       unnecessarily"