flood has 16 distinct synonyms spread across 8 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 rising of a body of water and its overflowing onto normally dry land
“plains fertilized by annual inundations”
an overwhelming number or amount
“a flood of requests”
light that is a source of artificial illumination having a broad beam; used in photography
the occurrence of incoming water (between a low tide and the following high tide)
“a tide in the affairs of men which, taken at the flood, leads on to fortune”
cover with liquid, usually water
“The swollen river flooded the village”
Synonyms, antonyms and the broader and narrower relations for flood come from Princeton University’s WordNet. Full sources and licences.
supply with an excess of
“flood the market with tennis shoes”
become filled to overflowing
“Our basement flooded during the heavy rains”