Also known as: ☢
A symbol used to warn people of the presence of radiation. It is a trefoil around a small inner circle.
This symbol is usually seen on containers used to store or transport radioactive substances. A typical public place where you might see this symbol is outside an X-Ray room at a Hospital.
On Danbooru, most commonly associated with Reiuji Utsuho for her ability to manipulate nuclear fusion.