Source : Webster's Revised Unabridged Dictionary (1913)

Half-and-half \Half`-and-half"\, n.
   A mixture of two malt liquors, esp. porter and ale, in about
   equal parts. --Dickens.

Source : WordNet®

half-and-half
     adj : in equal parts; "a half-and-half mixture"

half-and-half
     n : half milk and half light cream; contains 10% to 18%
         butterfat
     adv : in equal parts; "it was divided half-and-half"