2. Noun. A structural component of a vehicle, such as an automobile or aircraft, that uses a discrete, separate structure within a larger body-on-frame or unit body to carry certain components, such as the engine, drivetrain, or suspension. ¹
3. Noun. (Internet) One of the HTML frames that makes up a frameset. ¹
¹ Source: wiktionary.com
Definition of Subframe
1. a frame for the attachment of a finish frame [n -S]