WordWeb Online

1. According to circumstances
   "he was convicted circumstantially"
    
2. Insofar as the circumstances are concerned
   "the account was circumstantially accurate"
    
3. In minute detail
   "our inability to see everything circumstantially and clearly is due merely to the infirmity of our senses";
   - minutely
    
4. Without advance planning
   "they met circumstantially";
   - by chance, accidentally, unexpectedly

Antonym: advisedly