G = Gay - A man who is attracted to men; sometimes used to mean homosexual in general.
B = Bisexual - A man or women attracted to both genders.
T = Transgender - A person whose identity does not conform unambiguously to conventional notions of male or female gender roles, but combines or moves between these.
T = Trans-sexual - An individual who identifies with a physical sex that is different from their biological one
T = Two -Spirited - An individual who possesses a masculine spirit and a feminine spirit living in the same body
Q = Queer - Traditionally meant odd or unusual, though modern use often pertains to LGBT people. Its usage is considered controversial and underwent substantial changes over the course of the 20th Century with some LGBT people re-claiming the term as a means of self-empowerment.
Q = Questioning - a person who is questioning their gender, sexual identity or sexual orientation.
I = Intersex - Atypical combinations of physical features that usually distinguish male from female
A = Ally - Someone who supports the LGBT community.
References:
www.wikipedia.com
http://www.lgbtqia.org/LGBTQIA_at_UCSD/Welcome.html