Terminology

For a list of notations used within the wiki, please refer to the notation guide.

Outside of the wiki, the community as of 2018 tends to use Arcsys style notations.
In other words: Imagine an 8-way joystick. The bottom left is "1" and the top right is "9". "5" would be the stick is supposed at neutral - but in this instance, you can just type the button used for the attack.
For aerial attacks (), use a lowercase "j" followed by a period. For example, j.B
For running attacks (), use a lowercase "r" followed by a period. For example, r.B
For a string of attacks, list the buttons used for the string in order. For example, 2ABBBBA
For a combo involving Y-cancels () or multiple strings, put a space between them. For example, 4AABBB 2BAY 6AY j.Y

KnJ

Kawarimi no Jutsu, known in English as a Substitution. Newer players or those familiar with the Western releases will often call them subs.
This is the bread and butter of the GNT games: when you're locked in a combo, you can perform a KnJ at the cost of meter in an attempt to re-position yourself defensively behind the opponent.

LKnJ, RKnJ

A KnJ performed with or , respectively. In GNT4 onward, LKnJ simply has the player reappear behind the opponent, whereas the RKnJ is an "offensive" type KnJ where the player will attack as they reappear behind the opponent.

BT

Back turned - when your character is facing away from the opponent.

BTU

Back turned unblockable. This is an attack that hits the opponent’s back when the attacker is back turned. (BTUs are blockable if both players are back turned.)

BnJ

Billy no Jutsu. This is when a player turns around and throws a character that just performed an LKnJ. Named after a player named Billy (Purefunked), who pioneered the technique.

RnJ

Rob no Jutsu. This is when the player sidesteps an aerial RKnJ and throws the opponent as they land. Named after a player named Rob (Heartnana), who pioneered the technique.

OTK

One Tailed Kyuubi. Refers to Kyuubi Naruto, the undisputed best character in the game. Amusingly shares initials with the card game term One Turn Kill.

Tech roll

Often just called a tech, or an ukemi in other fighting games. Pressing or just before hitting the ground initiates a recovery roll (which is the term the Western Clash of Ninja titles use).

Throw tech

Often just called a tech, and also known as a throw break. Pressing , , , or right after an opponent attempts a throw to escape the throw. An unique animation occurs when this is correctly performed.

OTG

On the ground. This refers to when a character is laying on the ground. It also refers to when attacks hit a grounded character.

Crouch tech

Using the jump landing animation or certain attacks to crouch under jabs and other high attacks. Players of 3D fighters like Tekken may recognize this as what they call a high crush.

WuS

Wake-up Super. This is when a player performs a Super () move on a character that is standing up so the defending player cannot avoid the (usually) unblockable attack.

References

GNT4 Abbreviations and Terms. - Abbock, May 12, 2017