Invalidate (5)
'invalidate' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for rebut that I've seen before include "Deny claim" , "Brute (anag)" , "Rebuff; deny" , "Overturn" , "Confute" .)
'invalidate' is the definition.
(I know that invalidate can be written as annul)
This is the entire clue.
(Other definitions for annul that I've seen before include "Countermand" , "Cancel, revoke" , "Make invalid" , "Cancel or render void" , "Obligation" .)
'invalidate' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for revoke that I've seen before include "Annul by recalling" , "Officially cancel a decree" , "Retract" , "Annul (a decree)" , "Cancel (a decree, etc)" .)