Lewis & Short

Memmius, a, name of a Roman gens. mox Italus Mnestheus, genus, a quo nomine Memmi, Verg. A. 5, 117. So C. Memmius, a public man, who, being adjudged guilty of ambitus, went into exile to Athens, to him Cicero addressed several letters, and to him Lucretius dedicated his poem, De Rerum Natura; cf. Lucr. 1, 42.
Hence,

  1. A. Memmĭădes, ae, m., one of the Memmian gens, a Memmiade, a Memmius, Lucr. 1, 26.
  2. B. Memmĭānus, a, um, adj., of or belonging to a Memmius: praedia, of C. Memmius, Cic. Att. 5, 1, 1.