WordNet (r) 3.0 (2006):

lie down
    v 1: assume a reclining position; "lie down on the bed until you
         feel better" [syn: lie down, lie] [ant: arise, get
         up, rise, stand up, uprise]

Moby Thesaurus II by Grady Ward, 1.0:

28 Moby Thesaurus words for "lie down":
   bed, bed down, couch, crawl, curl up, go to bed, go to rest,
   grovel, lay, lie, lie flat, lie limply, lie prone, lie prostrate,
   loll, lounge, prone, prostrate, recline, repose, rest,
   settle to rest, snug down, sprawl, stretch out, supinate,
   take it easy, take life easy