neon

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A rare, inert gaseous element occurring in the atmosphere to the extent of 18 parts per million and obtained by fractional distillation of liquid air. It is colorless but glows reddish orange in an electric discharge and is used in display and television tubes. Atomic number 10; atomic weight 20.180; melting point -248.67°C; boiling point -245.95°C. See Table at element.
2. n. A neon tetra.
3. n. An extremely bright color.
4. adj. Extremely bright or vivid; fluorescent: neon purple.

Century Dictionary and Cyclopedia

1. n. An elementary substance occurring in gaseous form in the earth's atmosphere: atomic weight, 20. It was first isolated in 1898, and was obtained by the fractional distillation of liquid air. It is a colorless transparent gas which has been liquefied. Its boiling-point under normal pressure is—239° C. (—398.2° F.). In the gaseous state its density is 9.97 (hydrogen=1). In a tube suitably exhausted, electric discharge gives a characteristic spectrum, most of the lines of which are in the area of the visible red, with a specially noteworthy line at 5016 in the green. Neon is, like argon and the other recently discovered atmospheric gases, chemically inactive. It occurs in the air in larger proportion than any of the other gases of this class except argon—about 1 to 2 parts by volume in 100,000 of air.

Wiktionary

1. n. uncountable The chemical element (symbol Ne) with an atomic number of 10.
2. n. countable A form or sample of the element.
3. n. uncountable neon signs, collectively.
4. n. countable a neon tetra fish
5. adj. Extremely bright; fluorescent.

WordNet 3.0

1. n. a colorless odorless gaseous element that give a red glow in a vacuum tube; one of the six inert gasses; occurs in the air in small amounts