metalloid

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A nonmetallic element, such as arsenic, that has some of the chemical properties of a metal. Most metalloids behave as semiconductors.
• noun A nonmetallic element, such as carbon, that can form an alloy with metals.
• adjective Relating to or having the properties of a metalloid.
• adjective Having the appearance of a metal.

from The Century Dictionary.

• Relating to metalloids; like metal; having the form or appearance of a metal.
• noun In chem., a term which has been variously applied: as
• noun to the metallic bases of the fixed alkalis and alkaline earths, probably in consequence of their low specific gravity; and
• noun to all the non-metallic elementary substances.

from the GNU version of the Collaborative International Dictionary of English.

• adjective Having the appearance of a metal.
• adjective (Chem.) Having the properties of a nonmetal; nonmetallic; acid; negative.
• noun Formerly, the metallic base of a fixed alkali, or alkaline earth; -- applied by Sir Humphrey Davy to sodium, potassium, and some other metallic substances whose metallic character was supposed to be not well defined.
• noun Now, one of several elementary substances which in the free state are unlike metals, and whose compounds possess or produce acid, rather than basic, properties; a nonmetal; , are metalloids.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun chemistry An element, such as silicon or germanium, intermediate in properties between that of a metal and a nonmetal; especially one that exhibits the external characteristics of a metal, but behaves chemically more as a nonmetal.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective of or being a nonmetallic element that has some of the properties of metal