Abbreviation of 'Hot Mess Express'. A term describing the events, places, things surrounding amazing people mostly situated in Los Angeles and San Francisco CA.
Originally used to refer to 'pre-partying' also known as 'car-barring' before hot mess nights out.
"We're going to the club tonight. Get ready to be HMX!"
"It's 4PM on a Tuesday and you're drinking?" "HMX!"