step in

1 to make a brief visit I just stepped in to say hi on my way to class Synonyms come by, come over, drop by, drop in, pop (in), run (over), run in, call, stop (by or in), visitRelated Words barge (in); look up, see; bop (into), happen (by); frequent, hang (at), haunt, resort (to)

2 to serve as a replacement usually for a time only couldn't find anyone to step in for me so that I could take a break from my caregiving duties Synonyms fill in, pinch-hit, stand in, cover, sub, substitute, take overRelated Words understudy; relieve, spell; double (as)