vanilla
What does vanilla mean?
In kink, 'vanilla' means conventional, non-BDSM sex — and, by extension, a person who isn't into kink at all. It's not an insult by default; it's just the baseline flavour, the default setting. You'll hear it as an adjective ('vanilla sex,' 'a vanilla relationship') and as a noun for the person ('he's vanilla'). Plenty of people are happily vanilla, and plenty of kinksters enjoy vanilla play too. The word only gets a sting when it's used to mean 'boring.'
Origin
From vanilla as the 'default'/plain ice-cream flavour, borrowed into kink culture to mean conventional, non-BDSM sexuality.