And not definitely not. Right? (3)
I believe the answer is:
nor
'and not' is the definition.
('nor' means 'and also not')
'definitely not right?' is the wordplay.
'definitely not' becomes 'no'.
'right?' becomes 'r' (common abbreviation).
'no'+'r'='NOR'
(Other definitions for nor that I've seen before include "Common conjunction, goes with neither" , "Word paired with "neither"" , "Conjunction meaning 'and not'" , "Neither pairing" , "In addition, not" .)