semiversary 

6 month aniversary.

A shortened version of the word semianniversary.

On the inside of a card:
Happy semiversary

semiversary by KoH March 20, 2007

Sexiversary 

The date on which two people first had sex.

He was invited out for a drink after work, but he knew that since it was their sexiversary and she would be expecting him to be on his game, he declined.

Sexiversary by Kate Charlton June 18, 2008

Demiversary 

A demiversary is a "six month anniversary".

The term "six month anniversary" annoyed me enough to create the word "demiversary".
Joe and Jane Doe are having their demiversary.

Demiversary by comradeda August 28, 2011

Sepsiversary 

The anniversary of surviving a life-threatening sepsis event.

This week, I celebrated my 5-year sepsiversary.

Sepsiversary by Dan C. Gilliam December 8, 2017

Sexiversary 

The date on which two people first had sex.

He was invited out for a drink after work, but he knew that since it was their sexiversary and she would be expecting him to be on his game, he declined.

Sexiversary by Kate Charlton June 19, 2008

sexversary 

the anniversary of the day you had sex. most easily observed once pregnancy begins; in this sense, also known as conception day.

"happy sexversary, friend with benefits!"

"wow, amy and tom! happy sexversary, and welcome to the third trimester."

sexversary by janice jim July 13, 2009

Sepsiversary 

The annual celebration of surviving a sepsis event.

My 5-year sepsiversary is next month.

Sepsiversary by Dan C. Gilliam April 20, 2018