The Collaborative International Dictionary of English v.0.48:

Meridional \Me*rid"i*o*nal\, a. [F. m['e]ridional, L.
   meridionalis, fr. meridies midday. See Meridian.]
   [1913 Webster]
   1. Of or pertaining to the meridian.
      [1913 Webster]

   2. Having a southern aspect; southern; southerly.
      [1913 Webster]

            Offices that require heat . . . should be
            meridional.                           --Sir H.
                                                  Wotton.
      [1913 Webster]

   Meridional distance, the distance or departure from the
      meridian; the easting or westing.

   Meridional parts, parts of the meridian in Mercator's
      projection, corresponding to each minute of latitude from
      the equator up to 70 or 80 degrees; tabulated numbers
      representing these parts used in projecting charts, and in
      solving cases in Mercator's sailing.
      [1913 Webster]

WordNet (r) 3.0 (2006):

meridional
    adj 1: of or relating to a meridian
    2: located in the south or characteristic of southern people or
       places