MIB

On online auction and sales sites, MIB stands for "mint in box." This acronym means the listed item is in perfect condition and has not been removed from the box in which it came. Typically, it also means the box has not been opened.

You're most likely to encounter this acronym in listings for electronics and collectibles. Those items' condition can highly affect their value, so sellers use the MIB acronym to denote that the items are in mint condition (and should, accordingly, fetch a higher price).

Those discussing movies and/or science fiction may use MIB as shorthand for Men in Black. Based on a comic book series of the same name, the first MIB movie released in 1997, to popular acclaim. It was followed by three sequels, an animated series, and other various tie-ins.

Most of the MIB movies star Will Smith and Tommy Lee Jones, who play two agents (Agent J and Agent K) within a secret organization that polices alien life on Earth. In each movie, Smith and Jones must protect Earth from aliens who seek to either invade or destroy it, while also preventing the public from learning that aliens (many of whom are peaceful) live among them.