Metalloid

Formerly, the metallic base of a fixed alkali, or alkaline earth; -- applied by Sir H. Davy to sodium, potassium, and some other metallic substances whose metallic character was supposed to be not well defined.

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; as, boron, carbon, phosphorus, nitrogen, oxygen, sulphur, chlorine, bromine, etc., are metalloids.

Having the appearance of a metal.

Having the properties of a nonmetal; nonmetallic; acid; negative.

of or being a nonmetallic element that has some of the properties of metal; "arsenic is a metalloid element"