WordNet records no synonym and no antonym for lobe. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
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.
(anatomy) a somewhat rounded subdivision of a bodily organ or part
“ear lobe”
Synonyms, antonyms and the broader and narrower relations for lobe come from Princeton University’s WordNet. Full sources and licences.
(botany) a part into which a leaf is divided
the enhanced response of an antenna in a given direction as indicated by a loop in its radiation pattern
a rounded projection that is part of a larger structure