Source : Webster's Revised Unabridged Dictionary (1913)

Supplementation \Sup`ple*men*ta"tion\, n.
   The act of supplementing. --C. Kingsley.

Source : WordNet®

supplementation
     n 1: a quantity added (e.g. to make up for a deficiency) [syn: {supplement}]
     2: the act of supplementing [syn: {subjunction}, {subjoining}]