WordNet (r) 3.0 (2006):

curl up
    v 1: shape one's body into a curl; "She curled farther down
         under the covers"; "She fell and drew in" [syn: curl up,
         curl, draw in]

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "curl up":
   bed, bed down, bundle, couch, croodle, cuddle, cuddle up,
   go to bed, go to rest, lie down, loll, lounge, nestle, recline,
   repose, rest, settle to rest, snug down, snug up, snuggle,
   snuggle up to, sprawl, take it easy, take life easy