Definition of radon
: a heavy radioactive gaseous element formed by the decay of radium — see Chemical Elements Table
Test Your Vocabulary
Name That Color
-
- Name that color:

Can you spell these 10 commonly misspelled words?
TAKE THE QUIZ
A daily challenge for crossword fanatics.
TAKE THE QUIZLove words? Need even more definitions?
Merriam-Webster unabridged
Share radon
Time Traveler for radon
The first known use of radon was in 1918
See more words from the same year