tsundere 

Tsundere is a slang born on the Internet, and it is a word to describe the nature of female anime or game characters. Tsundere is a word combining two words, "Tsun Tsun" and "Dere Dere". Both terms describe attitudes of a person. "Tsun Tsun" is used for cold/blunt/curt attitude, while "Dere Dere" is used when a person becomes spoony in front of his/her lover.
(Definition is from the game " Tsuyokisu Cool×Sweet ")

Therefore, "Tsundere" is a female character who is usually cold, but she becomes spoony on her lover. Or, she is cold to the main character at first, but she becomes lovestruck later.

tsundere by rawr i'm a lion July 2, 2006

tsundere 

1: being on the surface sharp and sarcastic (tsuntsun) but underneath lovestruck and fawning (deredere); characteristic of a gap between acted out actions and feelings in mind;
2: normally being sharp but at some prompt suddenly becoming lovestruck; hot-cold personality type

そうやって俺のことを気にしつつ、しかし素直になりきれない、そのツンデレtsundereさが今若い男の間で大ブーム！

tsundere by grenciae December 22, 2008

Tsundere 

Japanese slang for one who is not nice and gets pissed off easily on the outside, but deep in the inside, is nice, caring, and gentle at all costs to the main character. It is usually used in anime/manga. The tsundere character usually shows his/her tsundere-ness in the later episodes/volumes/chapters.

Kagami Hirragi from the anime/manga Lucky Star is a great example of tsundere.

Tsundere by MisaTange July 8, 2009

Tsundere 

Tsundere describes someone who isn't very nice, but overtime changes to be nicer.

Or it could describe someone who deeply loves someone but tries to hide it from everyone.

Or it could mean some sadist bitch who beats the absolute shit out of the one she loves.

Boring as all hell main character: You're cute.

Tsun-chan: B-b-baaaaaka!

Boring as all hell main character's stupid pervy friend: What a tsundere.

Tsundere by Everythingphobic everythingist December 27, 2016

Tsunderella 

Crossover of the words Tsundere and Cinderella.

(Adj.) Tsundere: Typical anime arch-type girl. Usually one who tends to use violence means to resolve minor conflicts.

(Adj.) Cinderella: One whose attributes are unrecognised, or one who unexpectedly achieves recognition or success after a period of obscurity and neglect.

That prince of yours ain't gonna show up on his own, tsunderella.

Tsunderella by k4emic February 5, 2009

Tsundere 

Tsundere is a Japanese term for a character development process that describes a person who is initially cold (and sometimes even hostile) before gradually showing a warmer, friendlier side over time. The word is derived from the terms tsun tsun, meaning to turn away in disgust, and dere dere meaning to become 'lovey dovey'.

IT'S NOT LIKE I LIKE YOU OKAY! -Tsundere

Tsundere by Monika :3 June 11, 2018

Tsundere 

A cute ass boy or girl who doesn’t know how to express their feelings to you so they are mean instead

Girl: hey wanna walk to school together?
Tsundere: uh... sure.. but it’s not like I like you or anything! ..... dummy!

Tsundere by Greatlord Cthulhu November 28, 2020