your closest friend of the same sex, the person you'd be with if you were both homosexual.
*on the phone*
jack: "i miss you man, when are you coming home?"
phil: "next thursday...only 5 more days!"
jack: "i can't wait to see ya bro, i have so much to tell you...you've really been missin' out!"
phil: "i love you, man!"
jack: "i love you too, bro!"
*off the phone*
tina: "man, if i didn't know any better, i'd think you two were gay together!"
jack: "shut up! he's just my best friend, my bro, leave me alone!"
tina: "don't get so deffensive...i know you two are just hetero-lifemates."