unarch,v.|ʌnˈɑːtʃ| [un-2 3.] trans.andintr. To uncurve; to straighten. 1598Florio, Disarcare, to vnbend, to vnarche.1885Jefferies Open Air (1890) 234 His flexible back bends and undulates, arches and unarches, rises and falls as a wave rises and rolls on.