needful Copy link Outline 1. ŏpus, indecl. adj. (not used attributively)2. nĕcessārius (indispensably n.) • needful: 1. ŏpus, indecl. adj. (not used attributively): everything n., omnia quae opus sunt, Cato R. R. 14, init.: what is n. to be done, quid facto opus sit, Sall. Cat. 46 (quid adverbial): v. need. 2. nĕcessārius (indispensably n.): v. necessary.