Definition of "polyatomic" []

• Of or relating to a molecule that has three or more atoms as constituents. (adjective)

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.

• "Personally, I would call a polyatomic molecule only inelastic if its vibrations (or electrons) were excited, but as I say, this is debatable."
• "Following up on chriscolose's response: in dense gases you get "collision-induced absorption" - a pair of molecules can absorb a photon while they are close enough to be exerting forces on each other you can think of the two colliding diatomic molecules as forming a very short lived polyatomic molecule."
• "Any polyatomic molecules of interest in combustion would completely decompose even at much lower temperatures."