Definition of McClellan, George Brinton
- (1826–85), US army officer; known as Little Mac. He became general in chief of the US Army 1861 during the Civil War. Although he repulsed Lee at Antietam 1862, he was removed from command due to a lack of military aggressiveness. The Democratic presidential candidate in 1864, he was defeated by the incumbent Abraham Lincoln. He later served as governor of New Jersey 1878–81.