As you said, it means "kind of".
It's very informal and you won't find it in dictionaries.
In formal contexts, you can use "rather" with the same meaning, e.g.: It was rather cold.
Note: "kind of" is in the Merriam-Webster dictionary (see below).
"Kinda" is not.
Definition: 1:
to a moderate degree 2:
in a way that approximates : moreor less Synonyms: enough,
kindly [chiefly Southern],fairly, like, moderately, more orless, pretty, quite, rather,relatively, something, somewhat, sortof
english.stackexchange.com/users/212/b.roth
The Corpus of Contemporary American English (COCA) has 1650 incidences of kinda : TOTAL SPOKEN FICTION MAGAZINE NEWSPAPER ACADEMIC1650 172 1023 244 169 42
It is used overwhelmingly in fiction, and the few examples in newspapers and academic texts are almost exclusively in quotations of spoken English.
So, as the other answers have said, kinda is a pretty informal word, not used in formal texts except in quotations.
I personally would only use the word in very informal situations.
Its 1650 incidences in COCA are comparable to other adverbs, such as besides (1720), tight (1642), and regardless (1607).
As to whether or not it is an “actual” word, I think this is pretty clear evidence that it is.
As for its acceptability, it is listed in some dictionaries, including Random House and Merriam-Webster .
english.stackexchange.com/users/39/nohat
Wiktionary contains such words.
The entry for kinda ( http://en.wiktionary.org/wiki/kinda ) includes: kinda (colloquial) kind of
I kinda hafta do this right now.
That's kinda funny.
english.stackexchange.com/users/244/Peter Mortensen
The NOAD reports that kinda is an informal contraction of kind of ; it was first used in the early 20th century, and it was originally an American English alternation.
Kind of is an informal phrase for rather .
english.stackexchange.com/users/252/kiamlaluno
It is a word in spoken language and used in private letter-writing, but has not yet reached the level of recognition as standard language just as words like gonna, or "of" for have and others.
One more generation
and it is in dictionaries with a note about usage and in two generations it will be a normal variant.
english.stackexchange.com/users/63507/rogermue
Authorities at Oxford and Webster do not control or shape the English Language, they only define it.
In reality, the collective mind of every English speaker shapes the language.
And because some words have gained popularity in some groups and not others, the language has spread out into many dialects.
If you've ever read Mark Twain, you might have found his works difficult to understand as he wrote in the dialect of the Mississipi region.
Now imagine if all English speakers wrote in their own dialect.
We would all have to make a great effort to understand each other.
Authorities of the English language basically determine what words and grammatical structures
the majority of English speakers can understand, so that every English speaker can read books and other published works without trouble.
However, not everyone can understand their English.
My mother teaches in an inner city school and many of her students struggle in grammar because phrases like "Y'all goin' to the zoo
" sound perfectly fine to them as they are grammatically correct in their dialect.
So in short, "kinda" is a word, but not in the common dialect that English Authorities provide.
When writing, I would consider to what audience the work is intended for.
For example, if I were to write an article about the Packers and Bears rivalry, I would use it because people in the Midwestern United States commonly use it.
However I would replace it with a word like "rather" or find stronger diction if writing a formal and proper essay to an English Teacher.
english.stackexchange.com/users/127317/Matt Luettgen
I've used "kinda" as a word basically meaning "kind of" just run together. I wouldn't use it formally, but I noticed that Microsoft Word's spellchecker says that it isn't a word. I searched some and it seems that I'm not the only one who uses it, but it doesn't seem to be too popular.   So is it an actual word? How accepted is it?
Is "kinda" a word?
english.stackexchange.com
<word-choice><word-usage><is-it-a-word>
english.stackexchange.com/questions/3538
english.stackexchange.com/users/1325/Ullallulloo
"Kinda" is indeed a word but is very informal and you won't find it in dictionaries. Any examples in formal or academic texts will be almost exclusively in quotations of spoken English. "Kinda" is the contraction "kind of" and is thus the colloquial form of "kind of".  It is the alternative to "rather". It can be found in a wide number of  publications as well as in dictionaries such as the Merriam-Webster. The preference for its use can be personal, but generally its use informally is preferred. It has not achieved the recognition of standard English and very much remains in the domain of informal language. 
"Kinda" is indeed a word but is very informal and you won't find it in dictionaries. Any examples in formal or academic texts will be almost exclusively in quotations of spoken English. This means "kind of" and it is very informal and you won't find it in dictionaries. 'kinda'  is a pretty informal word, not used in formal texts except in quotations.
Although listed in some dictionaries, "kinda" is very informal and is used in spoken word and fiction. It is not used in formal texts. "Kinda" is indeed a word but is generally only accepted in informal settings or fiction. It will be very rarely found in formal or academic work and it may not be found in every dictionary.
"kinda" means "kind of" and is a colloquial form. It is the alternative to "rather" It is mainly used informally. There are a lot of uses in a wide range of publications. The choice of use is personal and can depend on target audidence.  It is also present in some dictionaries including the Merriam-Webster. The alternative is "rather" or another word if writing a formal essay.
This means "kind of" and it is very informal and you won't find it in dictionaries. kinda'  is a pretty informal word, not used in formal texts except in quotations.
"Kinda" is a very informal word and won't be used in formal settings. "Kinda is indeed a word, and is included in some dictionaries. "Kinda" is used a lot in fiction but not much in academic writing.