SUNGLASS
sunglass
(noun) a convex lens that focuses the rays of the sun; used to start a fire
Source: WordNet® 3.1
Etymology
Noun
sunglass (plural sunglasses)
singular of sunglasses; used chiefly in compounds
Noun
sunglass (plural sunglasses)
(archaic) A convex lens of glass for producing heat by converging the sun's rays into a focus.
Lighting a cigar with a sunglass — Hawthorne.
Source: Wiktionary
Sun"glass`, n.; pl. Sunglasses (.
Definition: A convex lens of glass for producing heat by converging the
sun's rays into a focus. "Lighting a cigar with a sunglass."
Hawthorne.
Source: Webster’s Unabridged Dictionary 1913 Edition