The Collaborative International Dictionary of English v.0.48:

Vasectomy \Vas*ec"to*my\ (v[a^]s*[e^]k"t[-o]*m[y^]), n. [Vas +
   -ecmoty.] (Surg.)
   Resection or excision of the vas deferens.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

vasectomy
    n 1: surgical procedure that removes all or part of the vas
         deferens (usually as a means of sterilization); is
         sometimes reversible

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "vasectomy":
   adenoidectomy, appendectomy, arteriectomy, castration,
   cholecystectomy, craniectomy, cricoidectomy, cystectomy,
   enterectomy, gastrectomy, hemorrhoidectomy, hysterectomy,
   mammectomy, mastectomy, mastoidectomy, nephrectomy, omphalectomy,
   oophorectomy, oophorocystectomy, orchidectomy, ovariectomy,
   pancreatectomy, penectomy, pericardiectomy, phrenicectomy,
   pneumonectomy, prostatectomy, salpingectomy, stapedectomy,
   tonsillectomy, ureterectomy, urethrectomy, venectomy