Source : Webster's Revised Unabridged Dictionary (1913)

Hydrogenation \Hy`dro*gen*a"tion\, n. (Chem.)
   The act of combining with hydrogen, or the state of being so
   combined.

Source : WordNet®

hydrogenation
     n : a chemical process that adds hydrogen atoms to an
         unsaturated oil; "food producers use hydrogenation to
         keep fat from becoming rancid"