Lewis & Short

Dĕcentĭus, ĭi, m., a general of Magnentius, Amm. 15, 6, 4; 16, 12, 5; Eutr. 10, 7.
Dĕcentĭăcus, a, um, adj., pertaining to Decentius.
Subst.:
Dĕcen-tiăci, ōrum, m., his adherents, Amm. 18, 9, 3.