subframe

Short definition from Wiktionary

Noun

1. 1
   A subsidiary frame (chunk of data).
2. 2
   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.
3. 3
   One of the HTML frames that make up a frameset.