WordNet sense 1 (subject to change):

changeable, uncertain

WordNet sense 2 (liable to or capable of change):

variable

WordNet sense 3 (not brought to a conclusion; subject to further thought):

open, undecided

WordNet sense 4 (unsettled in mind or opinion):

doubtful

WordNet sense 5 ((of groups of people) tending to travel and change settlements frequently):

mobile, mobile