WordWeb Online

1. Capable of or tending to change in form or quality or nature
   "mutable weather patterns"; "a mutable foreign policy";
   - changeable
    
2. Prone to frequent change; inconstant
   "the fickle and mutable nature of truth"; "the mutable ways of fortune"
    
3. Tending to undergo genetic mutation
   "It is likely, too, that the chromosomes of all eubacteria are as mutable as that of E. coli"
    
4. (programming, of a variable) having a value that can change during execution

See also: changeable, changeful, inconstant

Encyclopedia: Mutable