PRONUNCIATION: (ray-dee-oh-AK-tiv)

MEANING: adjective
1. Involving something extremely controversial that may rub off on others.
2. Spontaneously emitting radiation, as from an unstable atomic nucleus or in a nuclear reaction.

ETYMOLOGY: From French radio-actif, coined by Pierre and Marie Curie, from radio-, from Latin radius (beam, ray) + actif (active), from Latin activus (active). Earliest documented use: 1898.

GRAD: IO ACTIVE - the PhD candidate found signs of volcanos on one of the moons of Jupiter

RADIO ACT LIVE - no recordings when Jack Benny appeared Sunday evenings on WJZ, 770 on your dial

RADIO-LACTIVE - why you shouldn't nurse your baby if you've been exposed to fallout