welcome has 1 distinct synonym spread across 1 of its 6 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 2 recorded opposites are say farewell, unwelcome.
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.
accept gladly
“I welcome your proposals”
Synonyms, antonyms and the broader and narrower relations for welcome come from Princeton University’s WordNet. Full sources and licences.
receive someone, as into one's house
the state of being welcome
“don't outstay your welcome”
a greeting or reception
“the proposal got a warm welcome”
giving pleasure or satisfaction or received with pleasure or freely granted
“a welcome relief”