A "straight ally".
Used in some Gay-Straight Alliances and similar organizations to describe people who are not LGBT, but who want to promote LGBT
rights, protect LGBT's from
bullying, and/or simply want to reach out to a person who is LGB or T and let him/her know that s/he is in a safe place.
My best
friend is a transsexual and the world views her as an abomination. That's
one reason I'm a strally.
When I told my mom I was a strally in my university's GSA, she thought that a strally was a new kind of
lesbian.