Adjectives are words that describe things.
Some adjectives can describe words, such as adjectives.
Some adjectives can describe themselves. These are self-descriptive adjectives.

Some well known/suggested-by-other-noders self-descriptive adjectives:

I've only come up with these so far:

  • mispeled
There is a word, an adjective in fact, which describes self-descriptive adjectives. They are autological. There is another word that describes non-self-descriptive adjectives (all other adjectives). They are heterological.

A version of Russell's Paradox, called Grelling's Paradox, or sometimes, the Heterological Paradox, can be stated simply: Is "heterological" heterological?