The Collaborative International Dictionary of English v.0.48:

Swagbelly \Swag"bel`ly\, n.
   1. A prominent, overhanging belly. --Smollett.
      [1913 Webster]

   2. (Med.) Any large tumor developed in the abdomen, and
      neither fluctuating nor sonorous. --Dunglison.
      [1913 Webster]