Definition of radioactive
: of, caused by, or exhibiting radioactivity
Examples of radioactive in a Sentence
Uranium and plutonium are radioactive.
Recent Examples of radioactive from the Web
Its fuel and radioactive waste have been shipped away, and what’s left of the unit is monitored by Exelon.
Authorities say radioactive gases had accumulated within the reactor and leaked into the atmosphere.
They were driven onto Three Mile Island in a school bus, first donning yellow boots to protect their feet from possibly radioactive dust.
Large amounts of radioactive gas were released and confusion ensued.
Its fuel and radioactive waste has been shipped away, and what’s left of the unit is monitored by Exelon, the owner and operator of Unit 1.
But this rocket is temperamental, and as unstable as a radioactive isotope.
Most of the fallout quickly begins to decay, and scientists use what’s called the 7:10 Rule of Thumb to estimate radioactive risk: For every sevenfold increase in time after detonation, there is a 10-fold decrease in the exposure rate.
For 1.5 seconds, the sled screeches down its steel path, then smashes into a steel plate, ejecting the radioactive canister through an 18-square-inch steel aperture.
These example sentences are selected automatically from various online news sources to reflect current usage of the word 'radioactive'. Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.
Origin and Etymology of radioactive
International Scientific Vocabulary
First Known Use: 1898See Words from the same year
RADIOACTIVE Defined for English Language Learners
Definition of radioactive for English Language Learners
: having or producing a powerful and dangerous form of energy (called radiation)
RADIOACTIVE Defined for Kids
Definition of radioactive for Students
: caused by or exhibiting radioactivity a radioactive element
Seen and Heard
What made you want to look up radioactive? Please tell us where you read or heard it (including the quote, if possible).