Thrust.

Funny thing: thrusting doesn't do that much for me. Oh, it's not bad, I wouldn't kick thrusting out of bed for eating crackers, but it's not my preferred penetrative movement. When I masturbate there really isn't any in-out, just in-deep-and-grind. The feeling of something sliding around inside me does a lot more than the feeling of something sliding in and out of me. Sometimes, if a guy is well hung or using a big toy or lot of fingers, I don't even really need him to move.

I get the impression, though, that the in-out is pretty central to male pleasure (a lot of guys won't even stay hard for long without it), so I don't expect sex to be nothing but grinding. Which is fine, and even gets me off--both physically and in the feeling of being used. There's a certain brutal cachet to being pounded that nothing else can match, but on the level of pure sensation, I don't want a cock pounding me. I want it way in there massaging me.