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

Moby Thesaurus II by Grady Ward, 1.0:

66 Moby Thesaurus words for "esplanade":
   alameda, beaten path, beaten track, berm, bicycle path,
   billiard table, boardwalk, bowling green, bridle path, catwalk,
   dead flat, dead level, earth, fastwalk, flat, flatland, floor,
   foot pavement, footpath, footway, garden path, groove, ground,
   hiking trail, homaloid, horizontal, horizontal axis,
   horizontal fault, horizontal line, horizontal parallax,
   horizontal plane, horizontal projection, ledge, level, level line,
   level plane, mall, mean sea level, parade, parterre, path, pathway,
   plain, plane, platform, prado, prairie, promenade, public walk,
   run, runway, rut, sea level, sea of grass, sidewalk, steppe, table,
   terrace, towing path, towpath, track, trail, trottoir, walk,
   walkway, water level