Same Sex Soulmate
A term used to describe an intense friendship between two people of the same gender. Similar to "best friends", but more intense. These people complete each other, though they are not involved in a romantic, homosexual relationship. If one of them were of the preferential gender for a sexual connection, they would totally get married.
"Wow, M and B are really close these days." "Yeah, they're totally each other's same sex soulmate."