liberal has 15 distinct synonyms spread across 4 of its 7 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 conservative.
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.
showing or characterized by broad-mindedness
“a broad political stance”
tolerant of change; not bound by authoritarianism, orthodoxy, or tradition
given or giving freely
“was a big tipper”
a person who favors a political philosophy of progress and reform and the protection of civil liberties
a person who favors an economic theory of laissez-faire and self-regulating markets
1 of the 7 recorded senses carries no synonym, antonym or related term, so it is not shown above. Every sense, with its definition and examples, is on the full entry for liberal.
Synonyms, antonyms and the broader and narrower relations for liberal come from Princeton University’s WordNet. Full sources and licences.