What does "subframe" mean?

A subsidiary frame (chunk of data).

What is a synonym for "subframe"?

Common synonyms include: support frame.

noun

noun ·Rare ·Advanced level

Noun

1
A subsidiary frame (chunk of data).
"Four status bits accompany each subframe."
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.
"In the rebuilding no alterations have been made to the queen-post underframes except to add the subframe carrying the engine-transmission group."
3
One of the HTML frames that make up a frameset. Internet
"Specify the dimensions of your main frame and subframes and this online utility will create them for you."

"Four status bits accompany each subframe."

From sub- + frame.