a thin cylindrical pointed writing implement; a rod of marking substance encased in wood
"She sharpened the pencil until the wooden casing revealed the dark graphite core ready to write on paper."
graphite (or a similar substance) used in such a way as to be a medium of communication
"the words were scribbled in pencil"
"this artist's favorite medium is pencil"
a figure formed by a set of straight lines or light rays meeting at a point
"The pencil of parallel light rays passed through the small aperture in the window shutter."
a cosmetic in a long thin stick; designed to be applied to a particular part of the face
"an eyebrow pencil"
A paintbrush.
"He used an old pencil as a makeshift paintbrush to apply thick layers of acrylic on the canvas."
To write (something) using a pencil.
"She carefully penciled her notes onto the back of the envelope before handing it to him."
In plain English: To pencil something means to write it lightly with an eraser so you can change your mind later if needed.
"He decided to pencil his arrival time for tomorrow morning just in case traffic delays him."
The word "pencil" comes from the Old French pincil, which originally meant "small brush." This term is derived from the Latin pēnicillum, a diminutive form related to "tail" or "penis," and it is not connected to the word "pen.