Countersign vs Countersigning - What's the difference?

As verbs the difference between countersign and countersigning

is that countersign is to sign on the opposite side of (an instrument or writing) while countersigning is present participle of countersign.

is a second signature added to a document to affirm the validity of the signature of the first person.

(en noun)

a second signature added to a document to affirm the validity of the signature of the first person

The response to a sign or signal.

Only those who give the countersign may enter the Masonic Lodge.

(en verb)

To sign on the opposite side of (an instrument or writing).

(by extension) to add a second signature to a document, affirming the validity of the signature of another person