a sneak
When a girl is like, 'Yeah, I let you finger me in the ass,' but won't let you go all the way. Then you sneak your cock in there like a sneaky little thief and she's just like, 'Oh, okay.'
She said she wanted to try it, but when I pulled my fingers out, I slipped my cock in and she was like, 'Oh, that's nice.'
He did the sneak and she just kept going, like nothing happened.
She had her eyes shut and was like, 'Oh, that’s nice,' and then said, 'Just keep going.'