"Ideal" thing in science (3)

I believe the answer is:

gas

(Other definitions for gas that I've seen before include "It's not liquid or solid, like American petrol" , "could be embarrassing for American" , "Talk excessively" , "Oxygen maybe" , "State of matter not solid or liquid" .)

I've seen this clue in The Washington Post.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.