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]

Moby Thesaurus II by Grady Ward, 1.0:

85 Moby Thesaurus words for "dolmen":
   arch, barrow, beehive tomb, bone house, boundary stone, box grave,
   brass, burial, burial chamber, burial mound, bust, cairn,
   catacombs, cenotaph, charnel house, cist, cist grave, column,
   cromlech, cross, crypt, cup, cyclolith, deep six, dokhma,
   footstone, grave, gravestone, headstone, hoarstone, house of death,
   inscription, last home, long home, low green tent, low house,
   marker, mastaba, mausoleum, megalith, memento, memorial,
   memorial arch, memorial column, memorial statue, memorial stone,
   menhir, monolith, monstrance, monument, mound, mummy chamber,
   narrow house, necrology, obelisk, obituary, ossuarium, ossuary,
   passage grave, pillar, pit, plaque, prize, pyramid, reliquary,
   remembrance, resting place, ribbon, rostral column, sepulcher,
   shaft, shaft grave, shrine, stela, stone, stupa, tablet,
   testimonial, tomb, tombstone, tope, tower of silence, trophy,
   tumulus, vault