To celebrate in memory of a person who has passed away. Typically, this type celebration happens on the deceased's birthday or perhaps on an anniversary involving the deceased. The celebration should be a tribute to the lost friend and should include his/her favorite activities.
It is acceptable to add endings "-ing" or "-ed" to mournabrate to put the verb in the correct tense. Mournabration is the noun version of mournabrate.
Yo, today would have been Felipe's 21st birthday, so we have to mournabrate by pouring our forties out and getting blazed!