well has 10 distinct synonyms spread across 9 of its 22 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 2 recorded opposites are ill, badly.
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.
favorably; with approval
“their neighbors spoke well of them”
to a great extent or degree
“I'm afraid the film was well over budget”
with skill or in a pleasing manner
“she dances well”
without unusual distress or resentment; with good humor
“took the joke well”
a deep hole or shaft dug or drilled to obtain water or oil or gas or brine
in good health especially after having suffered illness or injury
“appears to be entirely well”
5 of the 22 recorded senses carry no synonym, antonym or related term, so they are not shown above. Every sense, with its definition and examples, is on the full entry for well.
Synonyms, antonyms and the broader and narrower relations for well come from Princeton University’s WordNet. Full sources and licences.
an enclosed compartment in a ship or plane for holding something as e.g. fish or a plane's landing gear or for protecting something as e.g. a ship's pumps