Black's Law Dictionary (2nd edition)dictionaries

Countersign

The signature of a secretary or other subordinate officer to any writing signed by the principal or superior to vouch for the authenticity of it Fifth Ave. Bank v. Railroad Co., 187 N. Y. 231, 33 N. E. 378, 19 L. R. A. 331, 33 Am. St Rep. 712; Gurnee v. Chicago, 40 UL 167 People v. Brie, 43 Hun (N. Y.) 326

Source: Black’s Law Dictionary 2nd Ed (1910)