( n. )
A plate with an opening, which is generally circular, used in instruments to cut off marginal portions of a beam of light, as at the focus of a telescope.
( n. )
A plate with an opening, which is generally circular, used in instruments to cut off marginal portions of a beam of light, as at the focus of a telescope.
Webster's Revised Unabridged English Dictionary. Пересмотренный полный словарь английского языка Webster. 2012