The yearly celebration of a person's first time trying or enjoying cannabis in some form. Sometimes celebrated by sharing one's cannabis or paraphernalia with members of their smoking community (reddit.com/trees, for example). Can also be celebrated with cannabis-infused space cake with candles.
Also, just another reason to get together with your stoner friends and get baked. Not to be confused with 4/20, the annual holiday that celebrates pot culture in general.
Miles invites his stoner circle over to his house every year at 4:20 on July 5th to celebrate his canniversary with them. They usually bring him gifts of rolling papers, a dub sack, and next year, they're going to Amsterdam for his canniversary!
N. The yearly anniversary of when you were canned (a.k.a. let go, downsized, considered redundant).
Alternate use: canniversary
I've decided to throw a Cannediversary Party to celebrate the day I was tossed out of that corporate Hellhole. All the ladies will wear pink slips, we'll serve canned foods, downsized items like mini weenies, have a bonfired and end it by letting some firedworks go off.