WordNet (r) 3.0 (2006):

rope off
    v 1: divide by means of a rope; "The police roped off the area
         where the crime occurred" [syn: rope in, rope off,
         cordon off]

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "rope off":
   bound, circle in, circumscribe, cordon, cordon off, define,
   delimit, delimitate, demarcate, determine, enclose, fix, isolate,
   lay off, mark boundaries, mark off, mark out, mark the periphery,
   quarantine, seal off, seclude, segregate, separate, set the limit,
   specify, stake out, surround