A visible suspension in the air of particles of some substance WordNet 3.0 & Open English WordNet

In physics, a vapor or vapour is a substance in the gas phase at a temperature lower than its critical temperature, which means that the vapor can be condensed to a liquid by increasing the pressure on it without reducing the temperature of the vapor. Wikipedia

Substance in the gas phase below its critical temperature. Wikipedia Disambiguation

A substance in the gas phase at a temperature lower than its critical point Wikidata