Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
sŭpĕr-addo, no perf., dĭtum, 3, v. a., to add over and above, to superadd (poet.; now usu. written separately): tumulo superaddite carmen, Verg. E. 5, 42: laurus superaddita busto, Prop. 2, 13, 33 (3, 5, 17): vitis, Verg. E. 3, 38.