noun
Usage: usually capitalized X
: astronomy dealing with investigations of celestial bodies by means of the X rays they emit
• x-ray astronomer noun , usually capitalized X
noun
Usage: usually capitalized X
: astronomy dealing with investigations of celestial bodies by means of the X rays they emit
• x-ray astronomer noun , usually capitalized X
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012