Definition of: irreversible

(ir′i·vûr′sə·bəl) adjective
1. That cannot be reversed or inverted.
2. Of, pertaining to, or designating a chemical or biological process which can continue only in one direction, as the coagulation of the white of a raw egg by heat, a degenerative disease, or the path of a stimulus along the nerves.
—ir′re·vers′i·bil′i·ty, ir′re·vers′i·ble·ness noun
—ir′re·vers′i·bly adverb