The Collaborative International Dictionary of English v.0.48:

Vagary \Va*ga"ry\ (v[.a]*g[=a]"r[y^] or v[a^]g"[.a]*r[-e]), n.;
   pl. Vagaries (v[.a]*g[=a]"r[i^]z or v[a^]g"[.a]*r[-e]z).
   [L. vagari to stroll about. See Vague.]
   [1913 Webster]
   1. A wandering or strolling. [Obs.]
      [1913 Webster]

   2. Hence, a wandering of the thoughts; a wild or fanciful
      freak; a whim; a whimsical purpose. "The vagaries of a
      child." --Spectator.
      [1913 Webster]

            They changed their minds,
            Flew off, and into strange vagaries fell. --Milton.
      [1913 Webster]

WordNet (r) 3.0 (2006):

vagary
    n 1: an unexpected and inexplicable change in something (in a
         situation or a person's behavior, etc.); "the vagaries of
         the weather"; "his wealth fluctuates with the vagaries of
         the stock market"; "he has dealt with human vagaries for
         many years"