1. adjective /ˈʌpsɛt,ʌpˈsɛt/
Angry, distressed or unhappy.
He is upset when she unfriends him on Facebook.
2. noun /ˈʌpsɛt,ʌpˈsɛt/
a) Disturbance or disruption.
My late arrival caused the professor considerable upset.
b) An unexpected victory of a competitor that was not favored.
"collision and upset": impact with another object or an overturn for whatever reason.
3. verb /ˈʌpsɛt,ʌpˈsɛt/
I’m sure the bad news will upset him, but he needs to know.
Introducing a foreign species can upset the ecological balance.
Wikipedia foundation.