An oxide containing three oxygen atoms per molecule. (noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "trioxide" in a sentence
"A refining facility handles this purification, and then chemically transforms the yellow cake into uranium trioxide, which is now suitable for FURTHER PROCESSING."
"The trioxide is a white powder readily dissolved by ammonia."
"The vapors would bond with any number of substances left by the finger—amino and lactic acids, glucose, potassium and carbon trioxide—and the resulting reaction created a visible print."