The the evil act of peeing in someone’s shampoo bottle and then not telling them. Leaves someone with pee in their hair for the duration they have that bottle.

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.