adjective
[more ~; most ~]
angry or unhappy
If you have an upset stomach, you have an unpleasant feeling in your stomach because of illness or because of something you have eaten.
verb
-sets; -set; -setting
[+ obj] to make (someone) unhappy, worried, etc.
to cause an unpleasant feeling in (your stomach)
to cause (something) to be unable to continue in the expected way
to defeat (someone who was expected to defeat you)
to cause (something) to fall
upset the apple cart
informal :to do something that changes or spoils a plan, situation, system, etc.
noun
plural -sets
[count] :an occurrence in which a game, contest, etc., is won by a person or team that was expected to lose
an unpleasant feeling of illness in your stomach [noncount]
a period of worry and unhappiness caused by something that has happened [count]