(organic chemistry) An organic compound with formula C₆O₂(OH)₄, consisting of a cyclohexadiene ring with four hydroxyl groups and two ketone groups in opposite (para) positions.

(mineralogy) A hard stone, such as the cat's-eye, which presents on a polished surface, and in the interior, an undulating or wavy light.

(geometry) Having the same perimeter; applied to the problem of finding a plane figure of the largest possible area whose boundary has a specified length

plural of sleeve