| arnold | (n) English poet and literary critic (1822-1888), Syn. Matthew Arnold |
| arnold | (n) United States general and traitor in the American Revolution; in 1780 his plan to surrender West Point to the British was foiled (1741-1801), Syn. Benedict Arnold |
| arnold-chiari deformity | (n) deformity in which part of the brain protrudes through the skull |
| arnold of brescia | (n) Italian theologian who censured the worldly possessions of monks and the temporal power of bishops and was condemned for dogmatic errors by the Second Lateran Council (early 12th century) |