Abbreviation for 'Fucking impossible, mate'. Coined by a developer in the early nineties, it is still widely used today.

Used to indicate that a(n often simple) development request cannot be completed.

Fuck it's Monday, similar to TGIF (thank God it's Friday) but used to describe the most miserable day of the week

Facebook Instant Messenger. Instant messaging in the social networking website called Facebook. It is commonly used to talk with people you may not want or feel like texting with. It is an informal conversation with others who you may not know very well as well as your good friends. It keeps you up to date with activity of the website which incorporates the facebook world to the user.
FIMing is the act of using FIM. It has become a popular term at San Diego State University where it originated.

Fart In Mouth

someone who is a genius and gets straight A's but also has a wicked life and isn't a nerd

Derived from the abbreviation FM, meaning Full Metal, Fim is a capture the flag player in JKA/JK3. Seated among the top North American players, Fim is often associated with the term "emo" due to his tendency to attempt to lower people's expectations of him by convincing them he sucks. Nobody knows why Fim does this with certainty especially considering that it almost never works due to Fim being one of the fastest players of the game. When confronted with this fact, he almost always responds with the same statement declaring that while his speed is substantial, he lacks any form of aim and can only be considered a good offense player at best. This, however, is also untrue as Fim is one of the best Base Defense players, a position that can, at times, require significant ability aiming.

Abbreviation (often used in text form) for "Fair is Muff" which in turn is slang for "fair enough". Similar adaptions to fair enough are Fairy's muff and Furry muff, spoken quickly to sound as much like fair enough as possible.