waxing has no recorded synonym. 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 waning.
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 application of wax to a surface
a gradual increase in magnitude or extent
“the waxing of the moon”
Synonyms, antonyms and the broader and narrower relations for waxing come from Princeton University’s WordNet. Full sources and licences.
(of the moon) pertaining to the period during which the visible surface of the moon increases
“the waxing moon passes from new to full”