/sub stich"ooh euhnt/ , n.
1. Chem. an atom or atomic group that takes the place of another atom or group present in the molecule of the original compound.
adj.
2. having been or capable of being substituted.
[ 1890-95; substituent- (s. of substituens ), prp. of substituere to SUBSTITUTE, equiv. to sub- SUB- + -stitu-, comb. form of statuere to set up, erect (see STATUE) + -ent- -ENT ]