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.