user wrote:
I'd continue to use them interchangeably .....
If during a positive control check the pilot corrects your call
of "spoilers," look under the wing for the extra control surface.

Yes, I've seen at least 2 books (FAA Glider Flying Handbook and Russell
Holtz's Glider Pilot's Handbook of Aeronautical Knowledge)where the
writer claimed that if the ..um.. "device".. extended top surface only
it was a spoiler and if it extended from both survaces it was an air
brake. Seems dubious to me.

Tony V LS6-b "6N"