mutable

Short definition from Wiktionary

Adjective

1. 1
   Changeable, dynamic, evolutive; inclined to change, evolve, mutate.
2. 2
   Having a value that is changeable during program execution.
3. 3
   Being one of the signs Gemini, Virgo, Sagittarius and Pisces, associated with adaptability, flexibility and sympathy.

Noun

1. 1
   Something mutable; a variable or value that can change.