built-in

1. Constructed as part of a larger unit; not detachable: a built-in cabinet.
2. Forming a permanent or essential element or quality: a built-in escape clause.

adjective

1. Serving as part of a whole, as a nondetachable part of a larger unit: component, constituent, incorporated. See include/exclude.
2. Forming an essential element, as arising from the basic structure of an individual: congenital, connatural, constitutional, elemental, inborn, inbred, indigenous, indwelling, ingrained, inherent, innate, intrinsic, native, natural. See be, native/foreign, start/end.

Definition: included
Antonyms: added, extra, not included

Built as an integral part of a larger construction, as furniture which is especially fitted in a building.

The adjective has one meaning:

Meaning #1: existing as an essential constituent or characteristic
  Synonyms: constitutional, inbuilt, inherent, integral