The definition of a break in is an illegal entry into a house, building or vehicle.
(noun)An example of a break in is a robbery of a store.
A break in is defined as the first usage or experience with something.
(noun)An example of break in is the first month of driving a new car.
See break-in in Webster's New World College Dictionary
noun
adjective
See break-in in American Heritage Dictionary 4
noun
Learn more about break-in