(n.) Slang.

Definition:
This literally means "delete" but can also be used as a digital middle finger.

Syntax:
When combined with an action before (if needed, otherwise absent) and then a target after (required), this command can be used as a diss, only understood by command line geeks. (Typically Linux users.)

Explanation:
The most proper use of this phrase has an instructional nature, such as, "go rm -rf yourself" and can be directed at an individual "rm -rf noob" or a group of people "rm -rf /noobs."

Origin:
From the UNIX command rm -rf /, used more loosely and can be artistically and freely expressed.

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.