Meaning of suppletion

sup•ple•tion

Pronunciation: (su-plē'shun), [key]
— n. Gram.
  1. the use in inflection or derivation of an allomorph that is not related in form to the primary allomorph of a morpheme, as the use of better as the comparative of good.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.