Wiktionary
a. Included in a system by default, as a standard, or at the time of construction.
Usage examples of "built in".
In addition, there are anywhere from five to twenty-five levels of offices, theaters, plumbing, air shafts, industrial plants, life-support machinery, recycling stations, and the like, built in shells around that inner section.
built into the other side of the passage's wall is a small control panel, very similar to the ones built into the nav-pits of the Power Wagons.
The voice emanated from the loudspeakers built into the entertainment center.
Bit by bit, they were chipping away at the hope she'd built inside her head.
He guessed that the shelter was built in the side of the hill running down to the Sound, and the embrasure peeped out through the hillside, providing natural ventilation but still safe from the blast of anything but a direct hit on the opening.