If you are referring to the legal terminology, setoff pertains to the demand made by the defendant against the plaintiff. It needs to be a valid legal claim that could be brought up as a separate suit and needs to be based on an entirely different claim from that of the plaintiff.

The plot in the film -The Little Rascals sets off Buckwheat and Porky.

Yes, look over your paperwork for the section on "Right to Setoff"

Pilcrow Sign (¶) used by MS Office Word to setoff a Paragraph.

Not from current Income.

But it can setoff the Capital Gains and hence Capital gains tax.