1 definition by SuspiciousFlag
Short for "Massive Sexual Indulgence", basically means masturbating or having sex without an end in sight, regardless of physical condition. Usually enacted by people who are high on the effects of strong drugs such as Black Tar Heroin.
"Hey bro, you free this weekend?"
"Nah man, I'm doing MSI"
"Bro, you gotta stop, it's just not healthy for you"
"Nah man, I'm doing MSI"
"Bro, you gotta stop, it's just not healthy for you"
by SuspiciousFlag September 9, 2019