A very good friend of yours that happens to be a male. Used in place of "boyfriend" to avoid uncomfortable situations.
Originated from having a "boy" that is a "friend," hence a "boy-friend." Eliminating the latter word leaving just "boy-" is pronounced "boy dash."
Straight guy #1: "I met this really awesome guy at college this semester. He's a really good boyfriend of mine."
Straight guy #2: "Woah bro. You're not gay, he's not your boyfriend. He's a really good boy dash of yours."
Girl #1: "Who's that?"
Girl #2: "Oh, that's John, one of my boyfriends."
Girl #1: "Wait, I thought you were dating Eric?"
Girl #2: "Yeah, I am. John's just a boy dash of mine."