Source : Webster's Revised Unabridged Dictionary (1913)

Metalloid \Met"al*loid\, a.
   1. Having the appearance of a metal.

   2. (Chem.) Having the properties of a nonmetal; nonmetallic;
      acid; negative.

Metalloid \Met"al*loid\, n. [L. metallum metal + -oid: cf. F.
   m['e]tallo["i]de.]
      (a) 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.
      (b) 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.

Source : WordNet®

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