WordNet sense 1 (a star that varies noticeably in brightness):

variable star

WordNet sense 2 (a quantity that can assume any of a set of values):

variable quantity

WordNet sense 3 (marked by diversity or difference):

varying

WordNet sense 4 (characterized by variety):

varied

WordNet sense 5 (changeable or inconstant):

versatile

WordNet sense 6 (subject to change):

changeable, uncertain, unsettled