Source : Webster's Revised Unabridged Dictionary (1913)

Hydroxyl \Hy*drox"yl\, n. [Hydro-, 2 + oxygen + -yl.] (Chem.)
   A compound radical, or unsaturated group, {HO}, consisting of
   one atom of hydrogen and one of oxygen. It is a
   characteristic part of the hydrates, the alcohols, the oxygen
   acids, etc.

Source : WordNet®

Ho
     n : a trivalent metallic element of the rare earth group; occurs
         together with yttrium; forms highly magnetic compounds
         [syn: {holmium}, {atomic number 67}]