1. marked by qualities giving the power to produce an intended effect

- written propaganda is less efficacious than the habits and prejudices...of the readers

- the medicine is efficacious in stopping a cough

Similar word(s): effective, effectual, efficacious, effective

2. producing or capable of producing an intended result or having a striking effect

- an efficacious law

Similar word(s): trenchant, impelling, impressive, telling, efficacious, efficient, potent, stiff, strong, powerful, useful, utile, effective, effectual