pace has 8 distinct synonyms spread across 7 of its 10 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 rate of moving (especially walking or running)
the distance covered by a step
“he stepped off ten paces from the old tree and began to dig”
the relative speed of progress or change
“he lived at a fast pace”
a unit of length equal to 3 feet; defined as 91.44 centimeters; originally taken to be the average length of a stride
walk with slow or fast paces
“He paced up and down the hall”
go at a pace
“The horse paced”
regulate or set the pace of
“Pace your efforts”
Synonyms, antonyms and the broader and narrower relations for pace come from Princeton University’s WordNet. Full sources and licences.