Real Dictionary

lambert in American English
the basic unit of luminance in the CGS system, equal to the brightness of an ideal surface that radiates or reflects light at the rate of one lumen per square centimeter (929.023 foot-candles or 10,000 lux or 1/π candela per square centimeter)
noun: a male given name: from Germanic words meaning “land” and “ bright”
noun: the centimeter-gram-second unit of luminance or brightness, equivalent to 0.32 candles per square centimeter, and equal to the brightness of a perfectly diffusing surface emitting or reflecting one lumen per square centimeter

lambert in British English
noun: Constant. 1905–51, English composer and conductor. His works include much ballet music and The Rio Grande (1929), a work for chorus, orchestra, and piano, using jazz idioms
noun: the cgs unit of illumination, equal to 1 lumen per square centimetre