loom has 6 distinct synonyms spread across 2 of its 5 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. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
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.
come into view indistinctly, often threateningly
“Another air plane loomed into the sky”
appear very large or occupy a commanding position
“The huge sculpture predominates over the fountain”
hang over, as of something threatening, dark, or menacing
“The terrible vision brooded over her all day long”
weave on a loom
“materials loomed in Egypt”
a textile machine for weaving yarn into a textile
Synonyms, antonyms and the broader and narrower relations for loom come from Princeton University’s WordNet. Full sources and licences.