Disrespectfully calling someone by their old name after they have changed their name. In particular, this is something done to transgender people.
"Well I've always known you as James, so I'm going to keep calling you James."
"Stop deadnaming me. My name is Jamie."
by happycookie August 3, 2015
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.
Don't call her by her deadname. She hasn't gone by that name in years.
by Canola Yogurt September 16, 2014
Deadname is a word used to describe someone’s old name after changing it (usually a trans person)
Don’t call her by her deadname
by Devil123457890 February 24, 2020
A Deadname is a Name a person under the Trans Umbrella used to have, but they changed it because it makes them uncomfortable.It is not okay to use a Person's Deadname, because they probably told you the name they prefer.
Person 1:hey *deadname*!
Person 2:hi could you please not use this name for me anymore its my Deadname I would like it more if you’d call me beanie.
Person 1:i’m sorry beanie
by I’m a hottie December 27, 2022
A deadname is the unused (birth)name of someone who changed their name, wether it has officially been changed or not. So technically, it's a dead name.

You could also call it a deadname because everyone who deadnames you shall become the dead /j
Person A: “Hi there deadname!”
Person B: “Oh hi! I probably didn't tell you yet but I changed my name to ______! I would appreciate if you used that name for me instead.”
by Juniper Woods kinnie June 21, 2021
Referring to someone by the name they were born with instead of the name they chose for themselves after their mental breakdown.
"Hey James!"
"I've told you before, my name is Jamie now. Stop deadnaming me."
"Shut the fuck up James. It doesn't matter that you've had your dick removed. That doesn't make you a woman, it just makes you a man without a dick. Now put the fucking kettle on."
by Pickle Flavoured Custard August 12, 2020
Deadnaming is the act of referring to a person by the name given by their parents, instead of by the name they chose for themselves later in life. It is considered by some to be an evil insult, and considered by others as a simple reference to who someone really is.
"If you grew up with Marilyn Monroe, and you call her Norma Jean, you are deadnaming her. Stop it, you evil monster!"
---------
"I demand that you call her Caitlyn from now on."
"But his name is Bruce. I would feel guilty if I ignored my conscience by purposely perpetuating a lie. I don't want to force myself to use a stage name as if it was real, or to pretend that someone is someone other than who they really are. If it upsets you when I use his real name or pronoun, then I will do my best to respect his feelings, and the feelings of others with your beliefs, by avoiding referring to him by EITHER name. And I will refer to him as "they/them" instead of "he/him"...but I refuse to refer to him as "she/her". I am doing my best to show respect to his feelings and yours, and I ask that you also respect MY feelings by not trying to force me to lie, and that you please stop trying to police my thoughts and beliefs with threats of cancellation."
by RealHonestDefinition June 26, 2022