also: いっぴつがき
noun
one-stroke sketch; unicursal drawing
Refers to a drawing made without lifting the pen or brush from the paper, often as a single continuous line. Can also describe a simple, quick sketch.
彼は一筆書きで猫の絵を描いた。
He drew a picture of a cat in one continuous stroke.
この図形は一筆書きで書け
Can this figure be drawn with a single stroke?