a cavity or passage in a tubular organ; "the lumen of the intestine"
a unit of luminous flux equal to the amount of light given out through a solid angle of 1 steradian by a point source of 1 candela intensity radiating uniformly in all directions
the position of the football player in the backfield who directs the offensive play of his team; "quarterback is the most important position on the team"
used of a height or viewpoint; "a commanding view of the ocean"; "looked up at the castle dominating the countryside"; "the balcony overlooking the ballroom"
a device for showing the operating condition of some system
a signal for attracting attention
(chemistry) a substance that changes color to indicate the presence of some ion or substance; can be used to indicate the completion of a chemical reaction or (in medicine) to test for a particular reaction