secesh adjective 1noun 1forms 1 adjective1 •(US, informal) Secessionist, supportive of the Confederacy during the United States Civil War.This is true, for Mrs. Sherman has an idea that St. Louis is unhealthy for our children, and because most of the Catholics here are tainted with the old secesh feeling. — 1864 noun1 •(US, informal) A secessionist, a supporter of the Confederacy during the United States Civil War.[…] our minds to get 'em, and we charged, yelling like bloody hl, drove the seceshes back a deuced sight quicker than they come, and popped 'em down at every shot. — 2010 formsseceshes