perennial

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Lasting an indefinitely long time; enduring.
• adjective Appearing again and again or year after year; recurrent: synonym: continual.
• adjective Botany Living three or more years.
• adjective Lasting or active throughout the year.
• noun Botany A perennial plant.
• noun Something that recurs or seems to recur on a yearly or continual basis.

from The Century Dictionary.

• Lasting or continuing without cessation through the year, or through many years: as, a perennial spring or fountain.
• Continuing without stop or intermission; perpetual; unceasing; never-failing; everlasting.
• In zoology, growing continually: noting teeth which have the pulp-cavity open, and grow indefinitely from persistent pulps: as, the perennial incisors of a rodent.
• In botany, continuing more than two years: as, a perennial stem or root.
• In entomology, forming colonies which are continued from year to year, as the ants, bees, and termites; also, living more than one year, as an insect.
• noun In botany, a plant which lives and blossoms or fructifies year after year.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Bot.) A perennial plant; a plant which lives or continues more than two years, whether it retains its leaves in winter or not.
• adjective ing or continuing through the year.
• adjective Continuing without cessation or intermission; perpetual; unceasing; never failing.
• adjective (Bot.) Continuing more than two years.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective Lasting or remaining active throughout the year, or all the time.
• adjective botany, of a plant Having a life cycle of more than two years. Compare annual, biennial.
• adjective figuratively Continuing without cessation or intermission; perpetual; permanent; unceasing; never failing.
• adjective figuratively Enduring; lasting; timeless.
• adjective figuratively Recurrent; appearing or recurring again and again.
• noun A perennial plant; a plant that is active throughout the year or survives for more than two growing seasons. Compare annual, biennial.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective lasting an indefinitely long time; suggesting self-renewal
• noun (botany) a plant lasting for three seasons or more
• adjective recurring again and again
• adjective lasting three seasons or more