Source : Webster's Revised Unabridged Dictionary (1913)

Turnip \Tur"nip\, n. [OE. turnep; probably fr. turn, or F. tour
   a turn, turning lathe + OE. nepe a turnip, AS. n[=ae]pe, L.
   napus. Cf. {Turn},v. t., {Navew}.] (Bot.)
   The edible, fleshy, roundish, or somewhat conical, root of a
   cruciferous plant ({Brassica campestris}, var. {Napus});
   also, the plant itself. [Formerly written also {turnep}.]

   {Swedish turnip} (Bot.), a kind of turnip. See {Ruta-baga}.
      

   {Turnip flea} (Zo["o]l.), a small flea-beetle ({Haltica, or
      Phyllotreta, striolata}), which feeds upon the turnip, and
      often seriously injures it. It is black with a stripe of
      yellow on each elytron. The name is also applied to
      several other small insects which are injurious to
      turnips. See Illust. under {Flea-beetle}.

   {Turnip fly}. (Zo["o]l.)
   (a) The turnip flea.
   (b) A two-winged fly ({Anthomyia radicum}) whose larv[ae]
       live in the turnip root.

Source : WordNet®

turnip
     n 1: widely cultivated plant having a large fleshy edible white
          or yellow root [syn: {white turnip}, {Brassica rapa}]
     2: root of any of several members of the mustard family