The UN says: Transphobia – “any form of prejudice or hostile attitude towards transgender people, including denying their gender identity or refusing to acknowledge it. Transphobia may be targeted at people who are or who are perceived to be trans, and may manifest as exclusion, stigma, harassment, criminalization, pathologization, discrimination and/or violence“. You can find this and other relevant definitions here: https://unfe.org/know-the-facts/definitions