Meaning : Run until the normal working temperature is reached.
Example :
We warmed up the car for a few minutes.
Meaning : Become more friendly or open.
Example :
She warmed up after we had lunch together.
Meaning : Cause to do preliminary exercises so as to stretch the muscles.
Example :
The coach warmed up the players before the game.
Meaning : Performing mild exercises to prepare for some more strenuous activity.
Example :
The singers have to warm up.
The marathon runner did not warm up and hurt himself.