Combination of "braking" (i.e., related to a car's brakes) and "breaking in period," describing the time it takes to adjust your foot to the sensitivity of the brakes of a car that you don't regularly drive, such as a friend's car, your spouse's car, or a rental car. At first, the brakes are either too sensitive, which causes you to slam down the breaks and jerk to a stop, or, too firm and require you to push down harder with your foot than you are used to.
by Ae5Ea8 April 15, 2015