tide has 2 distinct synonyms spread across 2 of its 6 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. Its one recorded opposite is ebb.
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 periodic rise and fall of the sea level under the gravitational pull of the moon
Synonyms, antonyms and the broader and narrower relations for tide come from Princeton University’s WordNet. Full sources and licences.
something that may increase or decrease (like the tides of the sea)
“a rising tide of popular interest”
there are usually two high and two low tides each day