The Collaborative International Dictionary of English v.0.48:

Rocket \Rock"et\, n. [F. roquette (cf. Sp. ruqueta, It
   ruchetta), fr. L. eruca.] (Bot.)
   (a) A cruciferous plant (Eruca sativa) sometimes eaten in
       Europe as a salad.
   (b) Damewort.
   (c) Rocket larkspur. See below.
       [1913 Webster]

   Dyer's Rocket. (Bot.) See Dyer's broom, under Broom.

   Rocket larkspur (Bot.), an annual plant with showy flowers
      in long racemes (Delphinium Ajacis).

   Sea rocket (Bot.), either of two fleshy cruciferous plants
      (Cakile maritima and Cakile Americana) found on the
      seashore of Europe and America.

   Yellow rocket (Bot.), a common cruciferous weed with yellow
      flowers (Barbarea vulgaris).
      [1913 Webster]

WordNet (r) 3.0 (2006):

Eruca sativa
    n 1: erect European annual often grown as a salad crop to be
         harvested when young and tender [syn: rocket, roquette,
         garden rocket, rocket salad, arugula, Eruca sativa,
         Eruca vesicaria sativa]