boron

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A soft, brown, amorphous or crystalline nonmetallic element, extracted chiefly from kernite and borax and used in flares, propellant mixtures, nuclear reactor control elements, abrasives, and hard metallic alloys. Atomic number 5; atomic weight 10.811; melting point 2,300°C; sublimation point 2,550°C; specific gravity (crystal) 2.34; valence 3. See Table at element.

Century Dictionary and Cyclopedia

1. n. Chemical symbol, B; atomic weight, 11. A chemical element belonging to the group of non-metals. Two allotropic forms of this element are known, one a brown, amorphous powder, slightly soluble in water, the other (adamantine boron) crystalline, and with a luster and hardness inferior only to that of the diamond. In all its compounds boron appears to be trivalent. It does not occur in nature in the free state, but some of its compounds are well-known articles of commerce. It is prepared by heating boric acid at a high temperature with some powerful reducing agent, such as potassium or aluminium. Its oxygen acid, horacic acid, and the soda salt, borax, are extensively used in the arts.

Wiktionary

1. n. The chemical element (symbol B) with an atomic number of 5; a metalloid

GNU Webster's 1913

1. n. A nonmetallic element occurring abundantly in borax. It is reduced with difficulty to the free state, when it can be obtained in several different forms; viz., as a substance of a deep olive color, in a semimetallic form, and in colorless quadratic crystals similar to the diamond in hardness and other properties. It occurs in nature also in boracite, datolite, tourmaline, and some other minerals. Atomic number 5. Atomic weight 10.81. Symbol B.

WordNet 3.0

1. n. a trivalent metalloid element; occurs both in a hard black crystal and in the form of a yellow or brown powder