Definition of "fractionation"

(chemistry) A separation process in which a certain quantity of a mixture is divided up into smaller quantities (fractions) in which the composition changes according to a gradient.  examples

(radiotherapy) The division of a total dose of radiation into fractions.  examples

(cryptography) A preliminary stage of encryption that divides each plaintext symbol into several ciphertext symbols.  examples

A form of hypnosis where the patient is made to enter and leave a trance state many times in quick succession.  examples