Something of very little importance is called trivial. 

The unexpected defeat of a favoured opponent is called an upset.

The division between two parts is called a schism.

To damage or harm something is to spoil it.

Threadlike structures within the human body cell are called chromosomes.

To act after something has happened is to show a response to that action.

The act of handing something in for a useful purpose is submission.

The visual inspection of something is called the view.

The discharge of a firearm is called a shot.

A short quick pull or movement is often called a twitch.