Lewis & Short

prōlūdĭum, ĭi, n. [proludo], preliminary exercise, training (late Lat.): cum quasi in proludiis negotium spectaretur, Amm. 28, 1, 10: cotidiana proludia exercitūs, id. 14, 11, 3: disciplinae castrensis, id. 16, 5, 10.