A term to describe the passing around of a drink (usually alcohol) in which everyone's mouth drinks from the same opening. This is very common in situations where people are looking to drink fast and don't have the luxury of cups.

The term is derived from the disease Mononucleosis (mono), otherwise known as "the kissing disease." Which is transferred by saliva from an infected person to the lucky recipient.

Monorail is also taken from other phrases such as "jump on the band wagon." However, this mode of transportation is a one railed train first invented in the early 1900s.

The phrase then is said to cue someone to take a drink, while joking that they going to get mono because another person, or many, have already drank from it.

When you get an old guy (preferably my g-pa) throw him on the ground and have him take a dump upwards like a train moving at high speed, and as the shit is coming upwards grab a condom and shove it over that then ram it in your ass like a monorail train thing.

SIDE NOTE: Lube might be helpful.

When a guy lays his hard penis on his belly and his girl slides her dripping wet pussy on top and glides along it like the Monorail at Disneyland.

1 : Partaking in intercourse aggressively enough that the other participant believes there are multiple partners.

2 : A one man train.

to pick a thin girl up and never let her touch the ground until you are finished. Also you can run train and never let her down just like a Monorail

To poop in another's butt and then have that person poop it back into your butt, poopetually.

A public works project that is a huge waste of taxpayer money that turns out to be either a scam, a huge waste of money or both.
Comes from the Simpsons episode "Marge vs the Monorail" where Springfield spent all their money on a monorail only to have it fall apart on its maiden voyage.