Or です in Hiragana. Desu is the polite form of the copula in Japanese linguistics. This translates out to "to be" or "is". It's usually used at the end of a sentence as the predicate, or is used to make a sentence sound more polite. The plain/casual form for this is "da", or だ. Sentences that use the copula usually take on the form of "A is B" type sentences, although it can take on other moods depending on the grammatical particles that accompany it.

Unfortunately, the copula has been bastardized and misused too often by people who don't know anything about Japanese. If you want to sound like a complete fucktard, use desu at the end of your sentences while speaking in English, or use it excessively at the end of every sentence, even when the sentence doesn't require it to be used.
E.g., 1 - Stative sense
僕は心理言語学の大学院生です/だ - Boku wa shinrigengogaku no daigakuinsei desu/da - I am a graduate student in psycholinguistics.

E.g., 2 - Confirmatory sense
この映画は素晴らしいですね?- Kono eiga wa subarashii desu ne? - This movie is great, huh/don't you think?

E.g., 3 - Interrogative sense
Me: 日本語を学んでいる - Nihongo wo manande iru - I am learning Japanese.
ネイティブ日本語話者 (Native Japanese speaker): 本当に?いつから学び始めたんですか?Hontou ni? Itsukara manabi hajimeta n desu ka? - Really? When did you start learning?
Me: えっと、約7ヶ月間前に始めたばかりです/だ ただ初心者です/だ - Etto, yaku nanakagetsu-kan mae ni hajimeta bakari desu/da. Tada shoshinsha desu/da - Well, I just started about 7 months ago. I'm just a beginner.
ネイティブ日本語話者: そうか?じゃ、頑張れ!- Sou ka? Ja, ganbare! - Is that so? Well, do your best!

E.g., 4 Improper use
Stupid person who doesn't actually know or isn't learning Japanese: OMG! Isn't that cat so kawaii desu^_^?
Me: 糞食らえ!英語で話せば、「Kawaii desu」って言うな 愚かな野郎 - Kusokurae! eigo de hanaseba, "kawaii desu" tte iu na. Orokana yarou - Eat shit! If you speak in English, do not say "kawaii desu", you stupid fucktard!
Stupid person: Nani? Speak English!
Me: てめえにそんな事言われたくない!- Temee ni sonna koto iwaretakunai! - Look who's talking, dickhead!
by Dr. Snark, PhD September 24, 2013
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1. Japanese for 'it is.' Often used at the end of sentences.

2. A huge 4chan meme that sorta went on to other sites. Suiseiseki, a character from the anime/manga Rozen Maiden, are nearly always mentioned. It usually is in motivational posters with Suiseiseki.
1. Kawaii desu!

2. Cheese, it is awesome, desu!
by MisaTange July 7, 2009
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The one word that every real Japanese person will go insane if you keep on saying it to them, mainly standing for 'it is' to go at the end of a sentence became a big meme of annoying weaboo or otaku. If you're wondering why it goes at the end of the sentence it's because in Japanese sentences are formed differently.

It is said in a motivational Poster that if you keep on typing Desu, you will turn Japanese, people believed that, and that's now what you will constantly hear from people who want to prove they're Japanese, also see kawaii for another annoying weaboo term.
by NatsukiKonaKon January 16, 2010
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A Japanese copula, or word used to grammatically link a subject and predicate.

It can be translated as "It is the case that -" or "It is for the reason that -". However, there is no English equivalent.

Alot of people use it at the end of sentences just to be cute.
Ashita doubutsuen ni iku n desu.
by Nieccie June 10, 2008
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The ancient cult originating from Mississauga that trains in the art of Yo-Yo's. Membership is hard to achieve, as the Desu Leader takes pride in his work. Therefore achieving membership is next to Impossible. DESU!!!!!
"Yo, are you in DESU?"
"Don't talk about this in public, you Yo-Yo!"
by Darkslayer23211 July 9, 2010
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A descriptor used to indicate that something is a bullshit knockoff of a part of Japanese culture. Can include poorly drawn anime, weeaboos, bad cosplay, and so forth. When in reference to a person, it should be followed by 'bitch', regardless of gender. When in reference to a thing, it should be followed by 'shit'.

Originates from the DESU meme, which involves spamming forums with the word 'desu' over and over again.
Jesus Christ, those fucking desu desu bitches in the room next to mine are STILL watching Death Note at 4 am.

Candy's drawing of a Yu-Gi-Oh orgy was some desu desu shit. I can't believe she handed it in for art class.
by syntheticxtasy September 28, 2011
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japanese for 'it is', often said at the end of sentences to seem cute or unwitting.
I went to the store and bought some milk, desu.
by jeremy February 6, 2003
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