The Collaborative International Dictionary of English v.0.48:

Mischance \Mis*chance"\, n. [OE. meschance, OF. mescheance.]
   Ill luck; ill fortune; mishap. --Chaucer.
   [1913 Webster]

         Never come mischance between us twain.   --Shak.
   [1913 Webster]

   Syn: Calamity; misfortune; misadventure; mishap; infelicity;
        disaster. See Calamity.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mischance \Mis*chance"\, v. i.
   To happen by mischance. --Spenser.
   [1913 Webster]

WordNet (r) 3.0 (2006):

mischance
    n 1: an unpredictable outcome that is unfortunate; "if I didn't
         have bad luck I wouldn't have any luck at all" [syn: bad
         luck, mischance, mishap]
    2: an instance of misfortune [syn: mishap, misadventure,
       mischance]

Moby Thesaurus II by Grady Ward, 1.0:

26 Moby Thesaurus words for "mischance":
   accident, adversity, blow, calamity, casualty, cataclysm,
   catastrophe, collision, contretemps, crack-up, crash, disaster,
   grief, ill hap, misadventure, misfortune, mishap, nasty blow,
   pileup, shipwreck, shock, smash, smashup, staggering blow, tragedy,
   wreck