watch has 25 distinct synonyms spread across 9 of its 13 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.
look attentively
“watch a basketball game”
follow with the eyes or the mind
“Keep an eye on the baby, please!”
be vigilant, be on the lookout or be careful
“Watch out for pickpockets!”
1 of the 13 recorded senses carries no synonym, antonym or related term, so it is not shown above. Every sense, with its definition and examples, is on the full entry for watch.
Synonyms, antonyms and the broader and narrower relations for watch come from Princeton University’s WordNet. Full sources and licences.
a period of time (4 or 2 hours) during which some of a ship's crew are on duty
a purposeful surveillance to guard or observe
the period during which someone (especially a guard) is on duty