The Collaborative International Dictionary of English v.0.48:

Abdominal \Ab*dom"i*nal\, a. [Cf. F. abdominal.]
   1. Of or pertaining to the abdomen; ventral; as, the
      abdominal regions, muscles, cavity.
      [1913 Webster]

   2. (Zool.) Having abdominal fins; belonging to the
      Abdominales; as, abdominal fishes.
      [1913 Webster]

   Abdominal ring (Anat.), a fancied ringlike opening on each
      side of the abdomen, external and superior to the pubes;
      -- called also inguinal ring.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Abdominal \Ab*dom"i*nal\, n.; E. pl. Abdominals, L. pl.
   Abdominales.
   A fish of the group Abdominales.
   [1913 Webster]

WordNet (r) 3.0 (2006):

abdominal
    adj 1: of or relating to or near the abdomen; "abdominal
           muscles"
    n 1: the muscles of the abdomen [syn: abdominal, abdominal
         muscle, ab]

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "abdominal":
   anal, appendical, big-bellied, cardiac, cecal, celiac, colic,
   colonic, coronary, duodenal, enteric, gastric, ileac, intestinal,
   jejunal, mesogastric, pyloric, rectal, splanchnic, stomachal,
   stomachic, ventral, ventricular, visceral