Posturing in a display of power and status to assert dominance over weaker, beta males, particularly in situations or contexts that rappers often find themselves. To maximize, inflate and obscenely flaunt one's strength, aggression, wealth, style, and pussy crushing ability to a degree that haters cower and feel less of a man in your presence.
"Come drink tequila in my VIP cabana pool" commanded the rapper to the set of hot Asian sluts, Flexin' Hard on some pussy-ass little boys and taking their bitches, shitting all over their day at Wet Republic.
A dong that is both hard and erect. Generally, when doing the sexy times, you'll probably want your dingle dong to be hard & erect. It's common practice within the male community to have a hard and erect dong when either masturbating, sexy sex, or moisturizing.
Guy 1: Man, when I sexed my boyfriend (no homo) last night, I had a Hard Erect Dong
Guy 2: Yeah same man, when I sexed my girlfriend (no hetero) last night, my dong was both hard and erect.
Guy 3: Shut up man we're at my father's funeral