in·con·stant /-stənt/
  (a.)易變的,不定的,無節操的,反復無常的
  In·con·stant a.  Not constant; not stable or uniform; subject to change of character, appearance, opinion, inclination, or purpose, etc.; not firm; unsteady; fickle; changeable; variable; -- said of persons or things; as, inconstant in love or friendship. “The inconstant moon.”
  While we, inquiring phantoms of a day,
  Inconstant as the shadows we survey!   --Boyse.
  Syn: -- Mutable; fickle; volatile; unsteady; unstable; changeable; variable; wavering; fluctuating.
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  inconstant
       adj : likely to change frequently often without apparent or cogent
             reason; variable; "inconstant affections"; "an
             inconstant lover"; "swear not by...the inconstant
             moon"- Shakespeare [ant: constant]