WordNet (r) 3.0 (2006):

bow out
    v 1: remove oneself from an obligation; "He bowed out when he
         heard how much work was involved" [syn: chicken out,
         back off, pull out, back down, bow out]
    2: retire gracefully; "He bowed out when he realized he could no
       longer handle the demands of the chairmanship" [syn: bow
       out, withdraw]

Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "bow out":
   abandon, abscond, beat a retreat, bundle, bundle off, depart,
   disappear, dismiss, duck out, egress, escape, evacuate, exit,
   get out, give the air, give the gate, go on furlough, go on leave,
   go out, hustle out, leave the scene, make an exit, march out,
   pack off, pass out, quit, remove, retire, retreat, run out,
   send away, send off, send packing, show the door, show the gate,
   slip away, slip off, slip out, sneak out, take leave, turn away,
   turn off, vacate, vanish, walk out, withdraw