shower has 7 distinct synonyms spread across 6 of its 11 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 plumbing fixture that sprays water over you
“they installed a shower in the bathroom”
washing yourself by standing upright under water sprayed from a nozzle
“he took a shower after the game”
a brief period of precipitation
“the game was interrupted by a brief shower”
someone who organizes an exhibit for others to see
a party of friends assembled to present gifts (usually of a specified kind) to a person
“her friends organized a baby shower for her when she was expecting”
spray or sprinkle with
“The guests showered rice on the couple”
take a shower; wash one's body in the shower
“You should shower after vigorous exercise”
provide abundantly with
“He showered her with presents”
Synonyms, antonyms and the broader and narrower relations for shower come from Princeton University’s WordNet. Full sources and licences.