The Collaborative International Dictionary of English v.0.48:

kistvaen \kist"vaen\ (k[i^]st"v[=a]n), n. [W. cist-faen.]
   (Archaeol.)
   A Celtic monument, commonly known as a dolmen.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

dolmen \dol"men\ (d[o^]l"m[e^]n), n. [Armor. taol, tol, table +
   mean, maen, men, stone: cf. F. dolmen.]
   A cromlech. See Cromlech. [Written also tolmen.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

dolmen
    n 1: a prehistoric megalithic tomb typically having two large
         upright stones and a capstone [syn: dolmen, cromlech,
         portal tomb]