So I guess you know what a full frame car is. Well a unibody is basically stamped steel rails that make up the "frame" between the sub-frames. There are a front and rear sub-frame. The rear subframe has all the rear suspension componets attached to it. This bolts to reinforced parts on the body. The front subframe consists of the K member (which I am not sure what the Exact def. is. but I know it refers to the engine cradle and the front subframe is the entire front suspension and engine.
So you could drop the front subframe and rear subframe and set the body on rollers if you wanted too.
Jeff