Someone who’s on the same side as you. Often used to describe someone who takes a stand against oppression or discrimination who is not a member of the oppressed group — for example, a white person who speaks out against racism or a straight person who speaks out against homophobia.
Someone who is a friend, advocate, and/or activist for LGBTQ people. A heterosexual ally is also someone who confronts heterosexism in themselves and others. The term ally is generally used for any member of a dominant group who is a friend, advocate or activist for people in an oppressed group (i.e. White Ally for People of Color).