perennial
     adj 1: lasting three seasons or more; "the common buttercup is a
            popular perennial plant" [ant: {annual}, {biennial}]
     2: lasting an indefinitely long time; suggesting self-renewal;
        "perennial happiness"
     3: recurring again and again; "perennial efforts to stipulate
        the requirements" [syn: {recurrent}, {repeated}]
     n : a plant lasting for three seasons or more
Source: WordNet® 2.0