step has 20 distinct synonyms spread across 12 of its 21 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the distance covered by a step
“he stepped off ten paces from the old tree and began to dig”
support consisting of a place to rest the foot while ascending or descending a stairway
“he paused on the bottom step”
a short distance
“it's only a step to the drugstore”
a mark of a foot or shoe on a surface
“the police made casts of the footprints in the soft earth outside the window”
a solid block joined to the beams in which the heel of a ship's mast or capstan is fixed
a sequence of foot movements that make up a particular dance
“he taught them the waltz step”
cause (a computer) to execute a single command
furnish with steps
“The architect wants to step the terrace”
move with one's feet in a specific manner
“step lively”
walk a short distance to a specified place or in a specified manner
“step over to the blackboard”
move or proceed as if by steps into a new situation
“She stepped into a life of luxury”
Synonyms, antonyms and the broader and narrower relations for step come from Princeton University’s WordNet. Full sources and licences.