a majestic peen is your penis but its a more stupid and goofy way of saying it. it is a long penis that amazes everyone and that your proud of. saying "majestic peen" instead of penis sounds way better and hilarious and always brings a laugh to the people around you or them shaking their heads thinking that your a complete retard.
"would you like to see my majestic peen?"
"oh my god I heard Emily has a majestic peen."
" eww Connor does not have a majestic peen."