In Zen Buddhism, an ensō (円相 , "circle"?) is a circle that is hand-drawn in one or two uninhibited brushstrokes to express a moment when the mind is free to let the body create.
The ensō symbolizes absolute enlightenment, strength, elegance, the universe, and mu (the void). It is characterised by a minimalism born of Japanese aesthetics.
image : Bhagavati words : Wikipedia