
kakkei gyuutou
This is not the first yo-ji that I've come across that befuddles my Japanese Kanji conversion software, but it is the first I've found that has interchangeable halves. Google tells me that this one is acceptable as either, 割鶏牛刀 or 牛刀割鶏.
Let's check the kanji to find out why:
割 is all about divisions. Read either 「かつ」 (meaning to divide, halve, cut, or any other form of dividing something, ranging from the mild "dilute," to the violent "Smash!") or 「わり」 (meaning the ratio, the proportion, or again "diluted with," for talking about drinks, as in CaptainのCola割り.
鶏 is (にわ)とり and is as straightforward as they come: chicken, of the domestic variety.
牛 is coincidental, I swear. Even though this is the year of the ox, I wasn't trying to foist any cow themed learnings on you. Besides, when it comes to the year, this kanji gets used: 丑. You might remember it from a lengthy post about why Japan is crazy for unagi on 土用の丑の日.
And last but not least, 刀, which most of you will recognize as "katana," and has popped up with a とう pronunciation at least once before on the Daily Yo-ji, in its very early days: 一刀両断 from all the way back in November of 2007.
Anyhow, I have an English equivalent expression for this rolling around in my head somewhere, but I can't seem to grasp it. のどがかゆい!

So I like to think of it as the inverse of that metaphor about "bringing a knife to a gun fight." 割鶏牛刀 is more like "bringing THIS GUN to a knife fight."
Definition:
牛を料理する大きな包丁で、鶏をさくという意味。伝じて、小さいことをするのに、大げさな道具や過分な力を用いること。
Translation:
Literal: Using a meat ax to carve a chicken.
1. Going to unnecessary and showy lengths to accomplish something simple.
2. Using a sledgehammer to crack a nut.
The thing that you want to keep in mind, if you ever have the chance to USE this expression, is that you probably shouldn't. Well, at least not in Yo-ji form. See, the problem is that the phrase 割鶏 (かっけい) is something you will NEVER come across in spoken Japanese. It's rare enough in written Japanese. So any usage of 割鶏牛刀 that I can find solves this problem by employing one of the much more common words that you can make with 割、namely 割く (さく;saku).
Like this: 「鶏を割くに牛刀,」 which means that in today's post, you've effectively learned one yo-ji and one non-yo-ji ことわざ. You're welcome!
例文 (loosely based on true events) :
Brett: coughs.
Fumiko: あなた、そこで横になって、少々お待ちしてね。
Lie down over there and wait, okay?
Brett: 何を?
For what?
Fumiko: 今先、救急車を呼んだから、着く前に死なないようにガマンしてください!
I just called for an ambulance, so PLEASE try not to die before they get here!
Brett:ええと、どういうことか?
Uh... What?
Fumiko: もう、近づかないでお願い!インフルエンザは映すものだわ!
STOP! Don't come any closer! Influenza is contagious!
Brett: おらー!インフルエンザに罹っとらんさ!救急車をカンセルしろお前!
What? I DON'T have the flu! Call off the ambulance!
Fumiko: あなた入院したほうがいいよ!
Babe, you should go to the hospital!
Brett: 咳のため、入院?鶏を割くに牛刀を用いんだぜ!
The hospital? For a cough? That's like amputating for a splinter!