From The Collaborative International Dictionary of English v.0.48 [gcide]:
crapper \crap"per\ (kr[a^]p"p[~e]r), n.
a toilet. [vulgar]
Syn: toilet, can, commode, pot, potty, stool, throne.
[WordNet 1.5 + PJC]
From WordNet (r) 3.0 (2006) [wn]:
crapper
n 1: a plumbing fixture for defecation and urination [syn:
toilet, can, commode, crapper, pot, potty,
stool, throne]