Source : Webster's Revised Unabridged Dictionary (1913)

Priceless \Price"less\, a.
   1. Too valuable to admit of being appraised; of inestimable
      worth; invaluable.

   2. Of no value; worthless. [R.] --J. Barlow.

Source : WordNet®

priceless
     adj : having incalculable monetary worth [syn: {invaluable}]