Plenteous, a.
Etymology: [From Plenty.]
1. Containing plenty; abundant; copious; plentiful; sufficient for every purpose; as, a plenteous supply. "Reaping plenteous crop." Milton.
2. Yielding abundance; productive; fruitful. "The seven plenteous years." Gen. xli. 34.
3. Having plenty; abounding; rich. The Lord shall make thee plenteous in goods. Deut. xxviii. 11.
Syn. -- Plentiful; copious; full. See Ample. -- Plen"te*ous*ly, adv. -- Plen"te*ous*ness, n.
Shades of meaning
Fernald has no entry of its own for plenteous; he lists it under plentiful.
He lists it without comment; the entries above explain its neighbors.