slip has 42 distinct synonyms spread across 20 of its 26 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 minor inadvertent mistake usually observed in speech or writing or in small accidents or memory lapses etc.
potter's clay that is thinned and used for coating or decorating ceramics
a young and slender person
“he's a mere slip of a lad”
a slippery smoothness
“he could feel the slickness of the tiller”
bed linen consisting of a cover for a pillow
“the burglar carried his loot in a pillowcase”
insert inconspicuously or quickly or quietly
“He slipped some money into the waiter's hand”
Synonyms, antonyms and the broader and narrower relations for slip come from Princeton University’s WordNet. Full sources and licences.
move smoothly and easily
“the bolt slipped into place”
move easily
“slip into something comfortable”
cause to move with a smooth or sliding motion
“he slipped the bolt into place”