illuminant

plural illuminants

1. Something that illuminates.

   They seemed to note the positions of the window at the one end and the door almost at the other, and even to take into account the single pendent electric light which up till then had been the sole illuminant.

   1914, Ernest Bramah [pseudonym; Ernest Brammah Smith], Max Carrados

   1 more example

   For a good many years, beginning in London, Brighton & South Coast days, the station at Heathfield, between Tunbridge Wells and Eastbourne, was lighted by natural gas. The use of this illuminant was discontinued about 1934.

   1946 July and August, “The Why and The Wherefore: Natural Gas at Heathfield”, in Railway Magazine, page 263

1. not comparableThat illuminates.