Source : Webster's Revised Unabridged Dictionary (1913)

Pineapple \Pine"ap`ple\, n. (Bot.)
   A tropical plant ({Ananassa sativa}); also, its fruit; -- so
   called from the resemblance of the latter, in shape and
   external appearance, to the cone of the pine tree. Its origin
   is unknown, though conjectured to be American.

Source : WordNet®

pineapple
     n 1: a tropical American plant bearing a large fleshy edible
          fruit with a terminal tuft of stiff leaves; widely
          cultivated in the tropics [syn: {pineapple plant}, {Ananas
          comosus}]
     2: large sweet fleshy tropical fruit with a terminal tuft of
        stiff leaves; widely cultivated [syn: {ananas}]