oniichan 

the Japanese word for "older brother" (younger brother is itouto).

Kiyoshi is my oniichan, Wakana is my oneechan.

oniichan by MishaMassacre August 19, 2007

Oniichan 

cool and smart and funny guy u should date him yees yes

Oniichan is so awesome i should be his gf.

Oniichan by notoniichan October 16, 2020

sexy_oniichan 

sexy_oniichan's a really amazing tiktoker. They have humor for others. Everyone loves them including me! they cheer everyone up, and are really amazing.

person 1: Have you seen sexy_oniichan's new tiktok?
person 2: Yeah, It really cheered me up!

sexy_oniichan by kazuhaswiife June 20, 2021

Wet Onii-chan 

Fucker who posts lolicon shit on manganelo. The Justin Y of mangas.

I saw another wet onii-chan post on the new isekai manga

Wet Onii-chan by gaylax October 13, 2021

Onii-Chan 

TLDR: Older Brother

A little more detail if you like-
Onii can end with 3 different Japanese honourifics, -San, -Chan, or -Sama.
-San is the basic ending for the basic big bro.
-Chan is a more compassionate ending for Onii if you really love your big brother and feel emotionally attached to him greatly
-Sama is a bit of a formal ending for big brother, nothing too special.

My Onii-San is a cool bro
I really love my Onii-Chan!
Yes he is my Onii-Sama

Onii-Chan by Rywen March 10, 2015

Onii-Chan 

Onii-Chan means "Big brother" in Japanese. Most people assume it's a mating call of some sort because of hentai but no that's just hentai. Lots of hentai has incest.

"Onii-chan! Drive me to my friend's house!"

Onii-Chan by RigsSaysGoodbye May 4, 2018

Onii-chan daisuki 

The phrase that welcomes you in the world of hentai.

Sora: Onii-chan daisuki! Be with me forever, onegai?
Haru: Ahhh Sora, that's incest.

Onii-chan daisuki by Vagini May 17, 2018