handiversary 

The annual celebration of the first time you pleasured yourself with your hand (AKA jerked it).

I'm going to get myself a new bottle of lotion to celebrate my handiversary.

handiversary by Jam1234567890 February 12, 2014

halfiversary

A couple's 6 month anniversary (similar to a half birthday).

Prem and Becky got married on July 11th, so they celebrated their halfiversary on January 11th.

halfiversary by Premdawg January 12, 2011

Heniversary 

The anniversary of a persons hen do. Usually this is celebrated by going on a night out and dressing up in traditional hen do attire.

Wow! Phoebe’s heniversary was so much fun!

Heniversary by Gibby, Guppy & Giblét September 6, 2023

Halfiversary

Like an Anniversary, but a celebration for six months in a relationship, friendship, etc..

Hey babe, its been six months! Happy Halfiversary!!

Halfiversary by Anonymously Jay October 13, 2016