When you take a soft pack of cigarettes, rip off the bottom and top, and light the entire pack at one time, puffing and blowing light a harmonica

n. The birth name of somebody who has changed their name. Most commonly attributed to trans people, but can be attributed to any person who has changed their name. (sometimes written as two words: dead name)

v. 1. To call somebody by their deadname.
v. 2. To out somebody's deadname to the public.