abbreviation of ultraviolet, by 1928.
"beyond the violet end of the visible spectrum," 1840, from ultra- "beyond" + violet. Ultra-red (1870) was a former name for invisible heat rays now called infra-red.
updated on September 28, 2017
utter
utterance
utterly
uttermost
U-turn
UV
uvea
uvula
uxorial
uxoricide
uxorious