N5168100 (nŏn′wûrd′)n. A sequence of letters or sounds that is not accepted as a word by speakers of a specific language, sometimes used in psychological or linguistic experiments.
nonword
(ˈnɒnˈwɜːd) n (Grammar) a series of letters not recognized as a word
non•word
(nɒnˈwɜrd)
n. a meaningless word or one that is not recognized or accepted as legitimate. [1960–65]