An unbelievably hard and most likely long shit that comes out of one's ass. The pain experience by "firing off" a shit missile is second to only explosive diarrhea and an assplosion. This is an immense amount of shit that forces tiself to come out in the most painful way possible.

A loud "spelunk" noise will occur when the missile has left the firing chamber.

The etymology of this term dates back not long ago when Metroid Prime 3: Corruption came out for the Wii. Since Samus's gunship was actually good for something other than saving and reloading this time, it shot missiles that were greatly helpful, yet majorly under used. The term "ship missile" is quite similar to "shit missile", and either a mispronunciation or a misspelling brought "Shit missile" to use.
HOLY FUCK!!!!!!!!!!!!!!

LET ME IN THE DAMNED BATHROOM, I HAVE TO LAUNCH A SHIT MISSILE!

(afterwards)

MOTHERFUCKER!!!! Son of a bitch, that hurt. *looks down*

Holy shit! It looks a meter long!
by DEC42 March 14, 2008
Get the shit missile mug.
When you take a shit in a plane and it shoots out and due to friction, catches fire.
by Kylin Kokus December 12, 2019
Get the Flaming Shit Missile mug.