What you get when a transsexual male tucks, tapes, or lashes his penis back sandwiching it between his legs. This word is where the affectionate term for a large meaty sandwich originiates, i.e. to have a lot of meat tucked between two buns.
Jason was about to hook up with a hot chick from the club but luckily as (s)he bent down he spotted her tranwich and quickly bolted.
Basically what you want your weight to identify as.
If you are a certain weight and you come out as transweight, you are saying you don't want to identify as the weight you are right now, and you want people to refer to your weight as something else.
I am coming out as transweight, I am no longer wanting to be a 300-pound man, and from now on, I will be referred to as having 140 pounds.