The Collaborative International Dictionary of English v.0.48:

Seaboard \Sea"board`\, adv.
   Toward the sea. [R.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Seaboard \Sea"board`\, n. [Sea + board, F. bord side.]
   The seashore; seacoast. --Ld. Berners.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Seaboard \Sea"board`\, a.
   Bordering upon, or being near, the sea; seaside; seacoast;
   as, a seaboard town.
   [1913 Webster]

WordNet (r) 3.0 (2006):

seaboard
    n 1: the shore of a sea or ocean regarded as a resort [syn:
         seaside, seaboard]