Outing is the act of revealing someone else’s transgender identity or sexual orientation without their consent or permission. Sometimes outing is intentional and sometimes it’s accidental, but by sharing information about someone’s gender identity against their wishes, you risk making them feel embarrassed, upset, and vulnerable. You may also put them at risk for discrimination and violence.
If someone shares their trans identity with you, remember that this is very personal information and it’s an honor that they trusted you enough to tell you. Always ask them what you’re allowed to share with others, and respect their wishes.
Definition from: https://www.plannedparenthood.org/learn/gender-identity/transgender