Nicklas, These are called autological words (autologs) – words having the property they denote, words that describe themselves. The opposite of an autological word is heterological word (heterologs) – a word not having the property it denotes. You wont find ‘autological’ and ‘heterological’ in most dictionaries although they did first appear in 1926 and are listed in the Oxford English Dictionary (see quote below). And Douglas Hofstadter's discussed ‘autological in his 1979 book ‘Gödel, Escher, Bach.’
Some further examples of AUTOLOGS are (in addition to your good ones of ‘noun, ‘grandiloquent,’ and ‘sesquipedalian’): English, polysyllabic, pentasyllabic, unhyphenated, understandable, visible, terse, descriptive, intelligible, unambiguous, pronounceable, readable, written, common, meaningful, definable, describable, repeatable, translatable, classifiable, memorizable, forgettable, unphonetic, unique, real, existent, post-Renaissance, Latinate, finite, avoidable, sibilant, asexual, numberless, harmless, uninspiring, unabbreviated, abecedarian, wee, antonym, thing, concept, abbr., unabbreviated, inoffensive, one, letters, nonpalindromic, UPPERCASE, CAPITALIZED.
Some examples of HETEROLOGS are: Italian, French, capitalized, long, tentacled, mono-syllabic, verb, oral, invisible, red, preposition, circular, misspelled, fat, truncated, unpronounceable, vowelless, question, backwards.
An interesting question to ask is if ‘autological’ is itself autological and if ‘heterological’ is itself heterological. If you assume that you know what ‘auto’ and ‘logical’ mean, so that you know that the word means self-sensical, then it could be considered autological. ‘Heterological,’ on the other hand is a bit more problematic. If you assume that it is not heterological, then it is not self-descriptive, which would mean that it is. So if it isn’t, it is! – and that’s a problem. If you go the other way and assume that it is heterological, then it is non-self-descriptive, which tells you that heterological doesn’t describe heterological, which means that it isn’t. So if it is, it isn’t! – and that’s also a problem! Sort of reminds one of an Escher staircase painting, doesn’t it?
< 1926 “Let us call adjectives whose meanings are predicates of them, like ‘short’, AUTOLOGICAL; others HETEROLOGICAL.”—‘Proceedings of the London Mathematical Society,’ F. P. Ramsey, XXV. page 358>
(Oxford English Dictionary, The Word Spy, http://www.stanford.edu/~segerman/autological.html
Ken G – June 22, 2004
Reply from Ken Greenwald (Fort Collins, CO - U.S.A.)