What is the meaning of a pre op transexual?

A transexual is someone who believes him or herself to be the other gender from the one he/she was born, and undergoes hormone therapy and surgery to change the appearance of the body to the other gender (gender reassignment surgery). A preop transexual is someone who has decided to undergo gender reassignment surgery, has started taking hormone therapy, and usually has been living as the other gender for 1-2 years and undergoing therapy, but has not yet had the surgery. The hormones can alter the appearance of the preop transexual, making them appear more like the other gender. For example, men taking female hormones can stop growing facial hair, lose muscle mass, and become less aggresive. Females taking male hormones can start getting facial hair, gain muscle mass, and have a deeper voice. Some preop transexuals decide to stop and this point and live as the other gender with the hormones, without undergoing surgery. After gender reassignment surgery, the person will then legally be the gender they have been altered to be.