Secret milk

An obscure reference to something sexual, different for everybody. Many times refers to cum/breast milk.

I can't tell you what the secret milk is, it's a secret.

Secret milk by Manure July 8, 2015

Milkman's Secret 

Taking someone up the ass. The "backdoor".

I turned her away from me, bent her over, and took the Milkman's Secret.

Milkman's Secret by MurderingRobot March 8, 2014