Solemnize is a verb that means to mark with a ceremony. 

The Latin word sollsemnis (suh LEM nis) means ‘customary.’ From this we get a word that refers to rituals performed at ceremonies. Solemnize has been with us since the Middle English period. Here’s an example of it in use:

After twenty years with the company, you’d think upper management would want to solemnize Eric’s service with some kind of dinner. But instead of a fancy ceremony, they just gave the poor guy a free cheeseburger and a coupon for a car wash.