The Collaborative International Dictionary of English v.0.48:

Esplanade \Es`pla*nade"\, n. [F. esplanade, Sp. esplanada,
   explanada, cf. It. spianata; fr. Sp. explanar to level, L.
   explanare to flatten or spread out. See Explain.]
   1. (Fort.)
      (a) A clear space between a citadel and the nearest houses
          of the town. --Campbell (Mil. Dict. ).
      (b) The glacis of the counterscarp, or the slope of the
          parapet of the covered way toward the country.
          [1913 Webster]

   2. (Hort.) A grass plat; a lawn. --Simmonds.
      [1913 Webster]

   3. Any clear, level space used for public walks or drives;
      esp., a terrace by the seaside.
      [1913 Webster]

WordNet (r) 3.0 (2006):

esplanade
    n 1: a long stretch of open level ground (paved or grassy) for
         walking beside the seashore