Source : Webster's Revised Unabridged Dictionary (1913)

Maypop \May"pop\, n. [Perh. corrupt. fr. maracock.] (Bot.)
   The edible fruit of a passion flower, especially that of the
   North American {Passiflora incarnata}, an oval yellowish
   berry as large as a small apple.

Source : WordNet®

maypop
     n : of southern United States; having an insipid berry the size
         of a hen egg [syn: {Passiflora incarnata}]