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”
put down or press the foot, place the foot
“For fools rush in where angels fear to tread”
Synonyms, antonyms and the broader and narrower relations for step come from Princeton University’s WordNet. Full sources and licences.
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”