upset has 28 distinct synonyms spread across 13 of its 17 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.
an unhappy and worried mental state
“there was too much anger and disturbance”
the act of disturbing the mind or body
“his carelessness could have caused an ecological upset”
a physical condition in which there is a disturbance of normal functioning
“the doctor prescribed some medicine for the disorder”
disturb the balance or stability of
“The hostile talks upset the peaceful relations between the two countries”
cause to lose one's composure
afflicted with or marked by anxious uneasiness or trouble or grief
“too upset to say anything”
thrown into a state of disarray or confusion
“troops fleeing in broken ranks”
2 of the 17 recorded senses carry no synonym, antonym or related term, so they are not shown above. Every sense, with its definition and examples, is on the full entry for upset.
Synonyms, antonyms and the broader and narrower relations for upset come from Princeton University’s WordNet. Full sources and licences.
defeat suddenly and unexpectedly
“The foreign team upset the local team”
having been turned so that the bottom is no longer the bottom
“an overturned car”