A penis, usually used in the context of sex, but this isn't a requirement.
Shaniqua: Oh Brutus how can I show you how much I care for you?
Brutus: You could be a champ and blow on my love-trumpet !
Shaniqua: That's true my love, I know you love your blow jobs !
Similar fo the Rusty Trombone just in reverse typical male and female fashion. The male rims out the women and commences diddling her piddle with multiple fingers in a trumpet like fashion.
Dave: What did you and Jill do last night?
Aaron: We started our own brass band!
Dave: She gave you a Rusty Tombone?!?
Aaron: And then I gave her the Rusty Trumpet!
Dave: NICE!!
Aaron: And then we each drank a bottle of Listerine so as to not get E-Coli.