A man dude refers to a man sitting next to you dude.
"Man dude we gotta do this."
if youre with friends and you see a hot girl you nudge your friends, nod in that girls direction and say man dude, your friends will then look and say man dude if they think shes hot
often happens in teenage years and most often in uk and america.
dave- "man dude"
pete- "yep man dude"
steve- "man dude definetly"