Disturbance or disruption.

“My late arrival caused the professor considerable upset.”

An unexpected victory of a competitor or candidate that was not favored to win.

(automobile insurance) An overturn.

“"collision and upset": impact with another object or an overturn for whatever reason.”

To make (a person) angry, distressed, or unhappy.

“I’m sure the bad news will upset him, but he needs to know.”

To disturb, disrupt or adversely alter (something).

“Introducing a foreign species can upset the ecological balance.”

To tip or overturn (something).

(of a person) Angry, distressed or unhappy.

“He was upset when she refused his friendship.”

(of a stomach or gastrointestinal tract, referred to as stomach) Feeling unwell, nauseated, or ready to vomit.

“His stomach was upset, so he didn't want to move.”