Perennial, a.
Etymology: [L. perennis that lasts the whole year through; per through + annus year. See Per-, and Annual.]
1. ing or continuing through the year; as, perennial fountains.
2. Continuing without cessation or intermission; perpetual; unceasing; never failing. The perennial existence of bodies corporate. Burke.
3. (Bot.)
Continuing more than two years; as, a perennial steam, or root, or plant.
1 more senses
Syn. -- Perpetual; unceasing; never failing; enduring; continual; permanent; uninterrupted.
1 other Webster entry under this spelling
Perennial, n. (Bot.)
A perennial plant; a plant which lives or continues more than two years, whether it retains its leaves in winter or not.
Shades of meaning
Fernald has no entry of its own for perennial; he lists it under eternal.
He lists it without comment; the entries above explain its neighbors.