|Image from wordables.com|
It turns out there is. Words that describe themselves are called “autological,” sometimes “homological”. 
Autological words I've already used are “multisyllabic”, "pentasyllabic", “unhyphenated”, “word”, “noun”, and “to verb”. All those words are instances of themselves. As I suppose is “mellifluous”.
“Yellow” is not yellow
Most words are heterological, that is to say their meanings don’t apply to them. “Long” is heterological because, as I noted at the top, it's not a long word. Likewise, the word “yellow” is not actually yellow, nor is the word “square” a square. 
Autological words seem to have a devoted fan base, and you’ll find lots of websites devoted to them. Indulge me while I mention a few more: “erudite” is erudite, “obfuscatory” (designedly unintelligible) is obfuscatory, and “recherché” (rare, exotic, or obscure) is recherché. “Terse” is terse, “twee” (impossibly cute) is twee, “prefixed” is prefixed, “adjectival” is adjectival, "pronounceable" is pronounceable. All of these I've found elsewhere, but one I've come up with myself is “noun phrase” which (if I remember my school grammar correctly) is a noun phrase.
I won't weary you with any more. Henry Segerman collects them. He has a list of clearly autological words, and a separate list of more doubtful cases. “Meaningful” is a doubtful case. Yes it has meaning, but is that enough? Surely to be meaningful you need an above average amount of it (which I don't think “meaningful” has). Judging from the internet evidence, coming up with autological words is meaningful to many people.
I'll end on a couple of curiosities. “Hellenic” is Hellenic, “English” is English, and “Afrikaans” is Afrikaans. But we must beware of being too quick to suggest others in this category. Is “Hebraic” Hebraic? “Swedish” certainly isn’t Swedish; nor is “German” German or “Dutch” Dutch, see the following table. Very few languages call themselves what English calls them. Afrikaans and Portuguese are rare exceptions. As are Indian languages - so far as I know, “Hindi”, “Urdu” and “Gujarati” are respectively Hindi, Urdu and Gujarati.
My last curiosity is this: does "heterological" describe itself? If so, it’s autological, because that’s what autological words do, they describe themselves. But wait! If "heterological" is autological, then it doesn't describe itself. Which makes it heterological; so it actually does describe itself, meaning it's autological. Welcome to the Grelling-Nelson Paradox. The link is to a Wikipedia article which I don't entirely follow. For example it casts doubt on whether “autological” is autological, which to my mind is indisputable.
Finally a thank you to Pat O’Conner & Stewart Kellerman of the grammarphobia blog. It's to them I turned when I first noticed that “to verb” and “word” are instances of themselves, and I wanted to know if there were other examples of this phenomenon, and is there a name for it. They sent a full reply from which most of the foregoing, and the notes below, are culled.
 The adjective “autological” originally had to do with self-knowledge when it first entered English in the 18th century. It came from the rare 17th-century noun “autology” (self-knowledge or the study of oneself), according to the Oxford English Dictionary.
But a new meaning emerged in the early 20th century, the OED says, when “autological” was used to describe a word, especially an adjective, “having or representing the property it denotes.”
The dictionary’s earliest recorded use of the word is from a paper by F. P. Ramsey published in 1926 in Proceedings of the London Mathematical Society: “Let us call adjectives whose meanings are predicates of them, like ‘short,’ autological; others heterological.”
 See article by the linguist Arika Okrent : http://theweek.com/articles/459441/17-words-that-describe-themselves. I've used several of her examples.