| vacuum headache | Headache due to closure of the frontal sinus. (05 Mar 2000) |
|---|---|
| vacuum pan | A device for growing crystals from solutions by gradually lowering the pressure within the sealed container holding the liquid. (09 Oct 1997) |
| vacuum tube | A glass tube from which the air has been removed, containing two or more electrodes, between which passes an electrical current or spark; used in the production of X-rays, or to control circuits. Previously in wide use, the vacuum tube has been supplanted by transistors in electronic circuits. (05 Mar 2000) |