(linguistics) An item that is memorized as part of a list, as opposed to being generated by a rule.Idioms such as "red herring" are listemes, as are irregular forms such as "geese".
2000, Steven Pinker, Words and Rules, A memorized chunk is sometimes called a listeme, that is, an item that has to be memorized as part of a list; one can argue that this book ought to have been called Listemes and Rules.