The name is given to someone of legendary status, who has proven time and time again that not only are they a legend, but they can compliment it with having a big dick. It is not necessary to see this person's penis to make this judgment as it can be proven by their legendary actions. It is a compliment and not to be confused with a homosexual greeting.
Someone who is a big dick legend usually gets absurdly drunk and proceeds to shout out, 'big dick legend' to anyone that cares to listen.
Mark: *drunk* Mannn .. Taxi driver your dick is so big no wonder it gets caught in the engine.
Taxi Driver: *silence*
Mark: You certainly are one big dick legend.
Dewy: Dude, got so wasted last night, told the bouncer he was a big dick legend and he was amused.
Mark: Haha, what a big dick legend.
Mark: You big dicked legend.
Dewy: BIG DICK LEGEND!
Jero: Guys, you all know I am a big dick legend.
Everyone: *looks away*
Jero: Fine, I am going back to masturbate in my Mercedes.
Jake: You Mercedes driving cunt!
Mark: Haha Jake, you big dick legend.
One who possesses both a big dick and legendary status. Generally drinks everyone under the table and then proceeds to inform everyone that they are also a big dick legend.
"Hey man, having a good night?!"
"BIG DICK LEGEND!"