va•porˈveɪ pər(n.)

1. a visible exhalation, as fog or smoke, suspended in the air.

   Category: Meteorology

2. a substance in gaseous form that is below its critical temperature.

   Category: Physics

3. a substance converted into vapor for technical or medicinal uses.

4. a combination of a vaporized substance and air.

5. gaseous particles of drugs that can be inhaled as a therapeutic agent.

6. Archaic. a strange, senseless, or fantastic notion. something insubstantial.

7. vapors, Archaic. mental depression or hypochondria. injurious exhalations supposed to be produced within the body, esp. in the stomach.

8. (v.i.)to rise in the form of vapor.

9. to emit vapor.

10. to talk pompously.

    Ref: Also, esp. Brit., vapour.

Origin of vapor:

1325–75; < L vapor steam

va′por•y(adj.)