The Collaborative International Dictionary of English v.0.48:

Dingey \Din"gey\, Dingy \Din"gy\, Dinghy \Din"ghy\, n. [Bengalee
   dingi.]
   1. a small boat propelled by oars or sails, used in the East
      Indies, in sheltered waters. [Written also dinghey.]
      --Malcom.
      [1913 Webster]

   2. a small boat intended to be used as a tender or lifeboat,
      carried or towed by a ship. It may be propelled by oars,
      sail, or a motor.
      [PJC]

   3. a small boat of shallow draft with cross thwarts for seats
      and rowlocks for oars with which it is propelled.

   Syn: dory, rowboat.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

dinghy
    n 1: a small boat of shallow draft with cross thwarts for seats
         and rowlocks for oars with which it is propelled [syn:
         dinghy, dory, rowboat]