What does "音痴 (Onchi)" mean in Japanese?

音痴（オン - チ) (On-chi) is a really useful Japanese word.

What does "音痴 (Onchi)" mean in Japanese?

おん‐ち【音痴】

1, To be unable to sing a song accurately because it is out of tune or pitch.

2, To be insensitive to certain things.

【Example】

JP) ゾロは方向音痴(ほうこう-おんち)だ。

/HoKo- Onchi/

EN) Zoro has no sense of direction.

方向音痴(ほうこう-おんち)

Source: ONE PIECE / 尾田栄一郎 / 集英社 / Jimmy Jimmy

【Example】

彼も方向音痴(Hoko-Onchi)だ。

He has also a crappy sense of direction.

Source: らんま1/2 / 高橋留美子 / ‎小学館 / 日本テレビ/ MAPPA

【Example】

Shinpachi is a bad/terrible singer.

新八は音痴(おんち/Onchi)だ。

Source: 銀魂 / 空知英秋 / 集英社 / テレビ東京 / サンライズ

【Example】

My manager is poor/bad/terrible at machinery.

私の上司は機械音痴 (きかい おんち)です。

/Kikai Onchi/

機械音痴 (きかい おんち) /Kikai Onchi/

運動音痴 (not athletic)

Nobita is not talented in sports./ Nobita is not athletic.

のび太は運動音痴 (うんどう おんち)だ。

/Undo Onchi/

運動音痴 (うんどう おんち) = (not athletic)

Onchi is such a useful word.

BUT!, the meaning is not good.

It is not recommended to use this word toward people as it has a bad meaning.

It may be used between close friends like "Cheeky bastard".