The Collaborative International Dictionary of English v.0.48:

Convex \Con"vex\, a. [L. convexus vaulted, arched, convex,
   concave, fr. convehere to bring together: cf. F. convexe. See
   Vehicle.]
   Rising or swelling into a spherical or rounded form;
   regularly protuberant or bulging; -- said of a spherical
   surface or curved line when viewed from without, in
   opposition to concave.
   [1913 Webster]

         Drops of water naturally form themselves into figures
         with a convex surface.                   --Whewell.
   [1913 Webster]

   Double convex, convex on both sides; convexo-convex.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Convex \Con"vex\, n.
   A convex body or surface.
   [1913 Webster]

         Half heaven's convex glitters with the flame.
                                                  --Tickell.
   [1913 Webster]

   Note: This word was often pronounced con-vex' by early
         writers, as by Milton, and occasionally by later poets.
         [1913 Webster]

WordNet (r) 3.0 (2006):

convex
    adj 1: curving or bulging outward [syn: convex, bulging]
           [ant: concave]

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "convex":
   arched, arciform, arclike, arcual, bandy, bellied, bellylike,
   bowed, bowlike, bulging, concave, convexed, embowed, excurvate,
   excurvated, excurved, gibbose, gibbous, humpbacked, humped, humpy,
   hunched, hunchy, out-bowed, oxbow, rotund, round, rounded,
   rounded out, vaulted