inconsistent

Short definition from Wiktionary

Adjective

1. 1
   Not consistent: Not compatible (with another thing); incompatible, discrepant, at odds.
2. 2
   Not consistent: Lacking internal consistency; self-contradicting; not compatible with itself.
3. 3
   Not consistent: Not consistent or coherent in thought or behavior.
4. 4
   Not consistent: Having the property that a contradiction can be derived.