Lewis & Short

sŭpĕr-ādĭcĭo, jēci, 3, v. a., to put in or add besides, to superadd (post-class.): quartam partem vini, Pall. Oct. 14, 15: piper his, Apic. 7, 4: decem dies observationi veteri, Macr. S. 1, 14.