[syn: by chance, accidentally, circumstantially, unexpectedly]
The Collaborative International Dictionary of English v.0.48:
Circumstantially \Cir`cum*stan"tial*ly\, adv.
   1. In respect to circumstances; not essentially;
      accidentally.
      [1913 Webster]
            Of the fancy and intellect, the powers are only
            circumstantially different.           --Glanvill.
      [1913 Webster]
   2. In every circumstance or particular; minutely.
      [1913 Webster]
            To set down somewhat circumstantially, not only the
            events, but the manner of my trials.  --Boyle.
      [1913 Webster]
WordNet (r) 3.0 (2006):
circumstantially
    adv 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 minutely
       and clearly is due merely to the infirmity of our senses"
       [syn: minutely, circumstantially]
    4: without advance planning; "they met accidentally" [syn: by
       chance, accidentally, circumstantially, unexpectedly]
       [ant: advisedly, by choice, by design, deliberately,
       designedly, intentionally, on purpose, purposely]