say it: suh-pluh-MEN-tur-ee
supplementary is an adjective meaning "functioning in a supporting capacity". It carries 2 recorded senses.
functioning in a supporting capacity
“the main library and its auxiliary branches”
Definitions, synonyms and semantic relations for supplementary come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.