The Collaborative International Dictionary of English v.0.48:

courgette \courgette\ n.
   1. a marrow squash plant whose fruit are eaten when small; --
      called also zucchini. [Chiefly Brit.]

   Syn: zucchini.
        [WordNet 1.5]

   2. a small cucumber-shaped vegetable marrow; typically dark
      green; -- called also zucchini. [Chiefly Brit.]

   Syn: zucchini.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

zucchini
    n 1: marrow squash plant whose fruit are eaten when small [syn:
         zucchini, courgette]
    2: small cucumber-shaped vegetable marrow; typically dark green
       [syn: zucchini, courgette]