The Collaborative International Dictionary of English v.0.48:

Convection \Con*vec"tion\, n. [L. convectio, fr. convehere to
   bring together; con- + vehere to carry.]
   1. The act or process of conveying or transmitting.
      [1913 Webster]

   2. (Physics) A process of transfer or transmission, as of
      heat or electricity, by means of currents in liquids or
      gases, resulting from changes of temperature and other
      causes.
      [1913 Webster]

            Liquids are generally heated by convection -- when
            heat is applied from below.           --Nichol.
      [1913 Webster]

WordNet (r) 3.0 (2006):

convection
    n 1: the transfer of heat through a fluid (liquid or gas) caused
         by molecular motion
    2: (meteorology) the vertical movement of heat or other
       properties by massive motion within the atmosphere

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "convection":
   communication, conduction, contagion, delivery, deportation,
   diapedesis, diffusion, dissemination, export, exportation,
   expulsion, extradition, import, importation, interchange,
   metastasis, metathesis, metempsychosis, migration, mutual transfer,
   osmosis, passage, passing over, perfusion, spread, spreading,
   transduction, transfer, transfer of property, transference,
   transfusion, transit, transition, translation, translocation,
   transmigration, transmigration of souls, transmission, transmittal,
   transmittance, transplacement, transplantation, transposal,
   transposition, travel