The Collaborative International Dictionary of English v.0.48:
Supplementation \Sup`ple*men*ta"tion\, n. The act of supplementing. --C. Kingsley. [1913 Webster]WordNet (r) 3.0 (2006):
supplementation n 1: a quantity added (e.g. to make up for a deficiency) [syn: supplement, supplementation] 2: the act of supplementing [syn: supplementation, subjunction, subjoining]