Using outside knowledge to solve problems. Ex. knowing a monster armor class or weakness from reading the book on your own time. Essentially knowing something or using knowledge your character wouldn’t know.

Rules Lawyer

A player who is really into following the rules and making sure others follow the rules. Often they are the ones thumbing through books to double check the rules.

Literally a roll you do to save your life in Dungeons and Dragons. For example, your reflex saving throw to see if you dodge a sudden trap, you use your will save o avoid being mind controlled or fortitude to avoid being poisoned.

Initative

A value that indicates your likelihood to go first. For example at the begining of a battle everyone rolls and adds there initative to see who goes first, second, thirs etc.

D20 System

A sysstem of using dice for dungeons and dragons. Rather than using a multitude of d6s like other games, in d&d you roll a d20 for pretty much everything your trying to do with other die for things like damage.  

Armour Class

A numerical value that represents how hard you are to hit/damge. It usually included your dexterity/ability to dodge, your armour and any magical shielding you have.

Hit Points 

In essance its how much damage you can take before dying. It is like your life bar in a video game represented in a numerical value.

Tabletop Role Playing Game

A game played in the real world, usually on a table. A game such as dungeons and dragons whrre you rile play a character, you arnt playing as yourself. Usually you are playing within a story written by one player rather than just miving around a board (board game). Usually played with books, character sheets and dice.

Multiple ability[score] dependant.

A chacter is mad when they rely heavily on 3 or more ability scores. Ex. A rouge-sorcerer would rely on dex int and cha heavily. A chacter that would be less M.A.D would be a wizard-rogue as they both need intelligence for there special abilities.