The Collaborative International Dictionary of English v.0.48:

Sea chickweed \Sea" chick"weed`\ (Bot.)
   A fleshy plant (Arenaria peploides) growing in large tufts
   in the sands of the northern Atlantic seacoast; -- called
   also sea sandwort, and sea purslane.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Arenaria peploides
    n 1: perennial succulent herb with small solitary axillary or
         terminal flowers [syn: seabeach sandwort, Arenaria
         peploides]