Nico Nico Ni 

It is a typical phrase of one of the characters of the animated series "Love Live", its original meaning is "Nico Smile" a song inherited from his father.

This phrase became famous to the "Nico" (character that says the phrase) to become an icon "Cancer" in Internet, and defining to the Weebs

It really does not have a use, it is more considered as a form of "meme"

¡Nico Nico Ni! -Doing something weird with hands-

Nico Nico Ni by A Love Live Elder but not weeb August 10, 2017

Nico-Nico-Niice 

(adj.)

A term referring to that one person in your group who is a self-proclaimed friendly person.

1. pleasant; agreeable; satisfactory; all in a really contradictory way.

"I'm a very friendly person you may not think so but I normally am Nico-Nico-Niice"

Nico-Nico-Niice by AngelShinken January 3, 2019

Nico Nico Chorus

A number of singers on the Japanese Nico Nico Douga site whose individual versions of the same song have been edited together in such a way that it appears that they are performing the song as one united chorus.

The song is usually (but not always) a vocaloid or anime song with a video backdrop, often with captions and/or icons identifying the individual singers.

Search for "Nico Nico Chorus" on Youtube for examples.

Nico Nico Chorus by greymousie January 18, 2011

Nico nico nii 

Serious definition: Nico Yazawa's catchphrase from the anime show Love Live! School Idol Project. Though this character seems mean and annoying at first glance, she uses this phrase often to cheer people up and show them that they don't need to feel sad, as they should always smile no matter the situation.

Nico nico nii~~ I'll nico nii your heart! I'm Yazawa Nico-Nico, and I'll put a smile in your heart! Remember, I'm Nico-Ni, and I love-Nico you!

Nico nico nii by ZAPBoy October 21, 2019

Nico nico kneecaps 

A very big threat, if someone threatens your nico nico kneecaps you best be runnin. Holds power over the reverse card. Unless you have Danny Devito on you, you're screwed.

This man breaks nico nico kneecaps, aight ima head out.

Nico nico kneecaps by Loaf that's not buttered yet November 25, 2019

Nico nico nii 

The phrase mentioned by Nico Yazawa, a member of the idol group μ's (pronounced "muse") in the anime, "Love Live! School Idol Project". It can either sound really cute or really annoying to you. No in-betweens.

Nico: "Nico nico nii!!"

Umi: "stfu bruh"

Nico nico nii by Syahrul Danial August 30, 2020

I'm gonna break your nico nico kneecaps 

What a weeb or otaku says when he's going to lay you out on the floor and he means it.

If I catch you trying to steal one of my anime figurines again, I'm gonna break your nico nico kneecaps.

I'm gonna break your nico nico kneecaps by sebacostamr January 6, 2019