The Collaborative International Dictionary of English v.0.48:

boardwalk \board"walk\ n.
   a walkway made of wooden boards; usually at a seaside. The
   more elaborate boardwalks at shore resorts are lined with
   many commercial retail establishments, on the side of the
   walk opposite the ocean. "On the Boardwalk in Atlantic City"
   [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

boardwalk
    n 1: a walkway made of wooden boards; usually at seaside

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "boardwalk":
   alameda, beaten path, beaten track, berm, bicycle path,
   bridle path, catwalk, esplanade, fastwalk, foot pavement, footpath,
   footway, garden path, groove, hiking trail, mall, parade, path,
   pathway, prado, promenade, public walk, run, runway, rut, sidewalk,
   towing path, towpath, track, trail, trottoir, walk, walkway