Flash Back Friday.

Typically used on a social media site, as a hashtag.

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.

Fake Boy Friend
(Usually acted by a childhood friend or a gay friend)

Female Best Friend- The best friend of yours that is a female.

Foul Bachelor Frog. An Advice Dog Spin-off. One of the only good ones, since almost all /b/tards can relate.

Foul Bachelor Frog, sometimes refereed to as "Facebook frog".

The FBF is a well know "meme" on 4chans /b/ random board, it is a picture of a bullfrogs head with a green pattern background, people add text on a website called meme generator that is agreeable and adheres to "foul bachelor behavior". This is one of the most popular memes on the /b/ board as many people who frequent /b/ can relate to it.

The text that people put on the picture is usually in a simple "event" - "reaction" context (see examples)

The text, when done properly usually contains a common, normally undesirable character trait being expressed, such as wearing dirty clothing, "fapping" (masturbating) into a sock, wearing a fapped into sock, microwaving a harddrive out of paranoia, not caring about surroundings, being disoriented about what time it is after an unexpected nap, etc. etc.