flow has 17 distinct synonyms spread across 10 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.
the amount of fluid that flows in a given time
any uninterrupted stream or discharge
the monthly discharge of blood from the uterus of nonpregnant women from puberty to menopause
“the women were sickly and subject to excessive menstruation”
be abundantly present
“The champagne flowed at the wedding”
undergo menstruation
“She started menstruating at the age of 11”
1 of the 14 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 flow.
Synonyms, antonyms and the broader and narrower relations for flow come from Princeton University’s WordNet. Full sources and licences.