NOUN (1)

1. a plant that lives in or on water;


ADJECTIVE (2)

1. relating to or consisting of or being in water;
- Example: "an aquatic environment"

2. operating or living or growing in water;
- Example: "boats are aquatic vehicles"
- Example: "water lilies are aquatic plants"
- Example: "fish are aquatic animals"

The Collaborative International Dictionary of English v.0.48:

Aquatic \A*quat"ic\, a. [L. aquaticus: cf. F. aquatique. See
   Aqua.]
   Pertaining to water; growing in water; living in, swimming
   in, or frequenting the margins of waters; as, aquatic plants
   and fowls.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Aquatic \A*quat`ic\, n.
   1. An aquatic animal or plant.
      [1913 Webster]

   2. pl. Sports or exercises practiced in or on the water.
      [1913 Webster]

WordNet (r) 3.0 (2006):

aquatic
    adj 1: relating to or consisting of or being in water; "an
           aquatic environment"
    2: operating or living or growing in water; "boats are aquatic
       vehicles"; "water lilies are aquatic plants"; "fish are
       aquatic animals" [ant: amphibious, terrestrial]
    n 1: a plant that lives in or on water

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "aquatic":
   aqueous, balneal, deep-sea, estuarine, grallatorial, hydrated,
   hydraulic, hydrous, liquid, littoral, natant, natatorial, natatory,
   plashy, seashore, shore, sloppy, splashy, swashy, swimming, tidal,
   water-dwelling, water-growing, water-living, water-loving,
   waterish, watery