Majestic Unicycle. u·ni·cy·cle [yoo-nuh-sahy-kuhl] noun 1. a vehicle with one wheel, especially a pedal-driven device kept upright and steered by body balance,  Majestic Unicycle u·ni·cy·cle [yoo-nuh-sahy-kuhl] noun 1 a vehicle with one wheel especially pedal-driven device kept upright and steered by body balance