I .
1.
to prepare for physical exercise or a performance by doing gentle exercises or practice
—related noun warm-up
2.
( of a machine, an engine, etc. ) to run for a short time in order to reach the temperature at which it will operate well
II .
warm up | ˌwarm sb/sth ↔ ˈup
to become more lively or enthusiastic; to make sb/sth more lively or enthusiastic :
The party soon warmed up.