The word you are thinking of is a semantic change. It's when a term takes on a new meaning, and it's this one is pretty new but calling someone "radical" in feminism & in the LGBT community is seen as "excluding trans people, sometime bi people as well".
I'll clarify since I realize I should have been more clear.. rad is short for radfem, aka radical feminist. Radical feminists believe in feminism, but they don't believe trans people are women & therefore not only don't deserve the same protection women have, they are a PROBLEM.
Most of them believe transgender people don't actually "exist" how they are. They think they're just "gay guys who have a sexual fetish for dressing up in women's clothes"(See: /r/ItsAFetish).