Most prominently used in Lauren Faust's reincarnation of My Little Pony show, Friendship is Magic, and its fans who call themselves bronies. It is a pony-speak for "ladies and gentlemen", or more appropriately, "boys and girls". It is related to somepony, anypony, everypony, etc.
"Fillies and gentlecolts! As mayor of Ponyville, it is my great pleasure to announce the beginning of the Summer Sun Celebration!"
-Mayor of Ponyville, The Mare in the Moon pilot episode.
A handsome guy Joe, saves a girl from getting hit by a car then gets her number and begins dating her. That would be an example of being 'gentlemental'.
A very sad way to say gentleman, mostly caused to mass depression or some kind of foreign intervention. If you ever use this word, seek immediate medical attention.
Bruce: "Can I help you with that?"
Julia: "What a sweet gentlement."
Bruce: "Nevermind, pick it up your damn self, you pustulent lump of grisly stomach acid."