pit has 20 distinct synonyms spread across 11 of its 14 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.
a concavity in a surface (especially an anatomical depression)
the hard inner (usually woody) layer of the pericarp of some fruits (as peaches or plums or cherries or olives) that contains the seed
“you should remove the stones from prunes before cooking”
(Christianity) the abode of Satan and the forces of evil; where sinners suffer eternal punishment
“Hurl'd headlong...To bottomless perdition, there to dwell”
(commodity exchange) the part of the floor of a commodity exchange where trading in a particular commodity is carried on
(auto racing) an area at the side of a racetrack where the race cars are serviced and refueled
a surface excavation for extracting stone or slate
“a British term for `quarry' is `stone pit'”
lowered area in front of a stage where an orchestra accompanies the performers
Synonyms, antonyms and the broader and narrower relations for pit come from Princeton University’s WordNet. Full sources and licences.