G'day Allen.
It looks like the Aussies are with the Brits on this one.
These are the 2 alternatives taken from the Macquarie dictionary (Australian
National Dictionary)
This usage is not unique to beekeeping in Australia.

rebate1
noun 1. a return of part of an original amount paid for some service or
merchandise; repayment, as of a part of charges.
verb (t) (-bated; -bating) 2. to allow as a discount. 3. to deduct (a
certain amount), as from a total. [Middle English, from Old French:
beat or put down]

rebate2
noun 1. a cut, groove, or recess made on the edge or surface of a board or
the like, as to receive the end or edge of another board or the like
similarly shaped.
verb (t) (-bated; -bating) 2. to cut or form a rebate in (a board, etc).
[Middle English, probably from Old French rabat a beating down, or
rabot a joiner's plane]

Paul