Emily Dickinson Lexicon

EF-FECT'U-AL, a.

1. Producing an effect, or the effect desired or intended; or having adequate power or force to produce the effect. The means employed were effectual. According to the gift of the grace of God given me by the effectual working of his power. Eph. iii.
2. Veracious; expressive of facts. [Not used.] Shak.
3. Effectual assassin, in Mitford, is unusual and not well authorized.