The operating of a newengine (especially that of a motor vehicle) at less than its normal speed until proper working has been established.
Wiktionary
Running-in Sentence Examples
I was running as fast as I could, but it was like I was running in slow motion.
Are you really running in boots?
The sound of water running in her bathroom brought her up short.
The men finished the fence and the goats are running in the south hills.
Railway transportation is supplied to Vermont by parallel lines crossing diagonally every part of the state at about equal intervals and running in general in a N.W.
