1. Plentiful, ample, abundant, bountiful describe a more than adequate supply of something. Plentiful suggests an over-adequate quantity: a plentiful supply. Ample suggests a more than adequate quality as well: to give ample praise. Abundant implies a greater degree of plenty, and bountiful a still more ample quality as well: an abundant, even a bountiful, harvest. 2. fruitful, bounteous, productive; luxuriant.