a sergio sandwich is when you get on the adjacent walls of someones room and turn the headboards towards the room and fuck at the same time, leading to the person in the middle room being sandwiched between you two
person 1: hey my girls coming over wanna hit a sergio sandwich later?
person 2: yeah he'll never see it coming
A term for one's significant other, to be used by adult heterosexual couples in long-term or lifelong, monogamous relationships who are serious, live together and have built their lives together, but have yet to get engaged or don't intend to marry at all.
Where "boyfriend/girlfriend" is too childish, "husband/wife" doesn't apply, "fiance" is dishonest, "partner" sounds homosexual and "lover" is too sexual, there is serioso. Coined by Chemda of the Keith and The Girl podcast, episode 130.