WordWeb Online

1. Capable of or tending to change in form or quality or nature
   - mutable
    
2. Such that alteration is possible; having a marked tendency to change
   "changeable behaviour"; "changeable moods"; "changeable prices"
   - changeful
    
3. Subject to change
   "a changeable climate"
   - uncertain, unsettled
    
4. Varying in colour when seen in different lights or from different angles
   "changeable taffeta"; "changeable silk"
   - chatoyant, iridescent, shot

See also: adjustable, astatic, changeability, checkered [N. Amer], chequered [Brit, Cdn], colorful [US], colourful [Brit, Cdn], distortable, erratic, exchangeable, fickle, fluid, inconstant, jittering, kaleidoscopic, kaleidoscopical, mercurial, mobile, open-ended, quick-change, quick-drying, quicksilver, reversible, unstable, variable, volatile

Antonym: unchangeable