Difficult to define exactly, but it's not the actual *name* of a situation or doctrine. Rather, it describes the outcome of a given action in the circumstances:
In the case of the US and USSR, their shared determination to retaliate to an attack by the other - given the size of their nuclear arsenals - would've assured mutual destruction.
by Richter September 20, 2003
mugGet the mutually assured destructionmug.

Reylo

A group of shippers who claim to hate the alt right, then ship an overpowered self insert character with a Neo Nazi
The alt right and Russian Robots said mean things about TLJ but I get hard when Ren murders people! Reylo4life!
by Richter January 22, 2020
mugGet the Reylomug.

don't be a stranger

Don't become a stranger. Usually said between friends when parting in anticipation of not seeing one another for a long time - when moving house, for example.

Is also often as a joke after marriage - warning the couple not to lose touch with their friends after becoming so attached - normally between men.
by Richter September 20, 2003
mugGet the don't be a strangermug.

gesundheit

German, meaning "health". Used to wish someone "health" after sneezing. It has been exported, but seems primarily to be used in the US. Similar is "bless you"
Achoo!

Gesundheit!

You get the idea.
by Richter September 07, 2003
mugGet the gesundheitmug.

fall on the grenade

To make a sacrifice for the good of others. Originally a military term for when a junior officer would deliberately fall to cover a grenade - the explosion from which would kill a far greater number of his side if he didn't. In particular, it would be when a junior officer would make this sacrifice for a senior one - to protect the commanding officer for the benefit (supposedly) of the army.

Its meaning has been expanded to cover things like taking the blame for a team-fuckup (eg. at work) or humpin a dawg so (as said above) your mates can get into the pretty ones.
by Richter September 25, 2003
mugGet the fall on the grenademug.