noun
: an incandescent lamp of constant and not necessarily known luminous intensity against which a working standard lamp and lamps to be tested are successively compared in a photometer
noun
: an incandescent lamp of constant and not necessarily known luminous intensity against which a working standard lamp and lamps to be tested are successively compared in a photometer
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012