WordNet (r) 3.0 (2006):

stay up
    v 1: not go to bed; "Don't stay up so late--you have to go to
         work tomorrow"; "We sat up all night to watch the election"
         [syn: stay up, sit up]

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "stay up":
   abide, await, bide, bide the issue, dally, dawdle, delay,
   dillydally, hang about, hang around, hold everything, hold on,
   hold your horses, linger, loiter, mark time, sit tight, sit up,
   stay, stick around, take time, tarry, wait, wait a minute,
   wait and see