Full Idea
A 'rebut' of an argument establishes that its conclusion is not the case. An 'undercut' of the argument shows that the premises do not support that conclusion.
Gist of Idea
You can 'rebut' an argument's conclusion, or 'undercut' its premises
Source
G. Aldo Antonelli (Non-Monotonic Logic [2014], 3.2)
Book Reference
'Stanford Online Encyclopaedia of Philosophy', ed/tr. Stanford University [plato.stanford.edu], p.11