St Valentine's Day Massacre 

a) an infamous massacre committed by Al Capone on St Valentine's Day 1929
b) when one breaks up with their significant other on St Valentine's Day

Do not commit a St Valentine's Day Massacre, definition b) , on your significant other.

St Valentine's Day Massacre by Uncle Dimma March 3, 2015

St Valentine's Day Massacre 

a) an infamous massacre committed by Al Capone on St Valentine's Day 1929

b) when one breaks up with their significant other on St Valentine's Day

Do not commit a St Valentine's Day Massacre, definition b) , on your significant other.

St Valentine's Day Massacre by Uncle Dimma December 8, 2014

St Valentine's Day Massacre 

(Referencing Al Capone's Valentine's Day Massacre of 1929)

When you break up with your girlfriend on St Valentine's Day.

If you are not a misogynistic son of a bastard do not commit a St Valentine's Day Massacre on your girlfriend.

St Valentine's Day Massacre by Uncle Dimma September 24, 2014

St. Valentine's Day Massacre 

Sex with a woman having her period.

When I was fucking her, she was having a st. valentine's day massacre. My "al capone" was all red.

St. Valentine's Day Massacre by mr. buggaloo October 1, 2004

St. Valentine's Day Massacre 

Have some girls get on their knees in a line. Proceed to take your pants off and bunny hop down the line, slapping the girls across the cheek with your cock.

Girls get down, I am about to perform the St. Valentine's Day Massacre

St. Valentine's Day Massacre by studmuffin March 7, 2005