1. (adj)effective, effectual, efficacious producing or capable of producing an intended result or having a strikingeffect "an air-cooled motor was more effective than a witch's broomstick for rapid long-distance transportation"-LewisMumford; "effective teaching methods"; "effective steps toward peace"; "made an effective entrance"; "his complaint proved to be effectual in bringing action"; "an efficacious law"
2. (adj)legal, sound, effectual having legal efficacy or force "a sound title to the property"