Definitions

1. noun

A unit of luminous flux, equal to the light emitted in a solid angle of 1 steradian by a source of one candela.

“The lamp produced a luminous flux of 100 lum.”

2. noun

The light or luminescence emitted by a glowing body, especially in the form of rays or a glow.

“The lum of the fire illuminated the dark room.”

3. noun

A small opening or vent, especially for light, air, or smoke, in a building or vehicle.

“The lum in the wall allowed for air circulation.”