Absolutely anything except 50% (3,4)
I believe the answer is:
not half
I believe this is a double definition.
'absolutely' is the first definition.
(both can mean 'extremely')
'anything except 50%' is the second definition.
(I've seen this before)
(Other definitions for not half that I've seen before include "missing 50%" , "less than fifty per cent" , "Very much, greatly" , "Forty nine per cent" , "Oh, yes!" .)