Vanilla, a bit like this definition. Not vanilla buttercream any way involved with BDSM.

He was a little more vanilla than I was used to, but we got along fine anyway. A member of the boring sexual majority, that has no idea of the raging sexual party of fetishes and swapping that whirls around them. When we walk up the street from the BDSM dungeon to get to the swinger’s party, let’s tone down the sexual talk and groping, we don’t want to scare all of the vanillas on the sidewalk. It’s the original of something, like the original Ice Cream flavour.