( a. )
Specifically, having such a combination of concave and convex sides as makes the focal axis the shortest line between them. See Illust. under Lens.
( a. )
Specifically, having such a combination of concave and convex sides as makes the focal axis the shortest line between them. See Illust. under Lens.
Webster's Revised Unabridged English Dictionary. Пересмотренный полный словарь английского языка Webster. 2012