Term: Minor Sentence

A Minor Sentence is one that does not necessarily have a main verb in it, but which can be understood as a complete unit of meaning.

Example:

 

'What time are you leaving?'
'Three.'

 

Here, Three is a minor sentence; it has no verb, but the listener will understand that the person means I am leaving at three o'clock.

Sentence fragment is another term with the same meaning.