mil has 8 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.
a Cypriot monetary unit equal to one thousandth of a pound
a unit of length equal to one thousandth of an inch; used to specify thickness (e.g., of sheets or wire)
a metric unit of volume equal to one thousandth of a liter
an angular unit used in artillery; equal to 1/6400 of a complete revolution
Synonyms, antonyms and the broader and narrower relations for mil come from Princeton University’s WordNet. Full sources and licences.