(n.) One who wavers; one who is unsettled in doctrine, faith, opinion, or the like.

Chilopoda Chordata Echiuroidea Ectoprocta Entoprocta Milquetoast Monoplacophora Nemertinea Phoronidea baby big baby chicken chicken liver coward crybaby doormat dull tool fence-sitter fraid-cat fraidy-cat funk funker gutless wonder invertebrate lightweight lily liver meek soul milksop mollycoddle mouse mugwump namby-pamby nebbish nonentity pansy pantywaist pushover sad sack scaredy-cat shilly-shally sissy softling softy sop waverer weak sister weakling white feather white liver wobbler