A substance diffused or suspended in the air, especially one normally liquid or solid. The morning sun caused the dew to turn into vapor, rising gently from the grass.
A visible exhalation, such as fog, mist, steam, smoke, or noxious gas, diffused through or suspended in the air. The cold air made the vapor from his breath visible as he spoke.
An attack of faintness, depression, or nervous anxiety (chiefly in the plural form 'the vapors', archaic). She claimed to suffer from the vapors whenever unpleasant news was mentioned.