lumper has 8 distinct synonyms spread across 1 of its 2 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 splitter.
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.
a laborer who loads and unloads vessels in a port
a taxonomist who classifies organisms into large groups on the basis of major characteristics
Synonyms, antonyms and the broader and narrower relations for lumper come from Princeton University’s WordNet. Full sources and licences.