The Collaborative International Dictionary of English v.0.48:

Amputation \Am`pu*ta"tion\, n. [L. amputatio: cf. F.
   amputation.]
   The act of amputating; esp. the operation of cutting off a
   limb or projecting part of the body.
   [1913 Webster]

WordNet (r) 3.0 (2006):

amputation
    n 1: a condition of disability resulting from the loss of one or
         more limbs
    2: a surgical removal of all or part of a limb

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "amputation":
   abscission, anastomotic operation, annihilation,
   bloodless operation, butchering, capital operation, chopping,
   cleavage, compensating operation, corneal transplant,
   crescent operation, cutting, destruction, dichotomy,
   elective operation, elimination, emergency operation, enucleation,
   eradication, excision, exclusion, exploratory operation,
   extinction, extirpation, fenestration operation, fission,
   heart transplant, interval operation, kidney transplant,
   laceration, major operation, minor operation, mutilation,
   operation, organ transplant, organ transplantation,
   palliative operation, radical operation, removal, rending,
   rescission, resection, ripping, scission, section, severance,
   slashing, slicing, splitting, surgery, surgical intervention,
   surgical operation, surgical technique, tearing, the knife,
   transplant