noun
radiation warning sign; trefoil; radiation warning symbol
Refers to the internationally recognized symbol indicating the presence of ionizing radiation, often a magenta or black trefoil on a yellow background.
実験室のドアに放射能標識が貼ってある。
A radiation warning sign is posted on the laboratory door.
放射能標識を見たら、その区域には近づかないでください。
If you see a radiation warning symbol, please do not approach that area.
Compound of 放射能 (radioactivity) and 標識 (sign, marker). The term is a straightforward technical compound with no known historical irregularities.