WordWeb Online

1. Not done with purpose or intent
   "an unwitting mistake may be overlooked"
   - unintentional, unplanned
    
2. Not aware or knowing
   "an unwitting subject in an experiment"
    
3. Unaware because of a lack of relevant information or knowledge
   "his rudeness was unwitting"
   - ignorant, unknowledgeable, unknowing

See also: incognisant [Brit], incognizant, unaware, uninformed, unintended, unwittingly

Antonym: witting