pencil

1. (now chiefly historical) A paintbrush.Examples: "But living art may not least part expresse, / Nor life-resembling pencill it can paynt[…]."; "why is it not lawfull for every man to pourtray himself with his pen, as it was for him to doe it with a pensell?"; "He requested three things of Sir Joshua Reynolds:—To forgive him thirty pounds which he had borrowed of him; to read the Bible; and never to use his pencil on a Sunday."historical

2. (optics) An aggregate or collection of rays of light, especially when diverging from, or converging to, a point.

3. (geometry) A family of geometric objects with a common property, such as the set of lines that pass through a given point in a projective plane.Examples: "When, by the pencil becoming oblique to the surface, the vergency produced on the pencil becomes changed, the primary and secondary focal points, V and H, separate […]"; "A drillable robot is capable of placing its end link in any orientation in the pencil of planes containing its first link."; "Let l and m be two hyperparallel lines. All the transversals to l and m that form congruent corresponding angles with l and m lie in a pencil."

4. (medicine, obsolete, rare) A small medicated bougie.obsoleterare

5. (gambling) Ellipsis of power of the pencil.Examples: "And most important of all, Cully now had 'The Pencil', that most coveted of Las Vegas powers."abbreviationalt-ofellipsis