It's difficult to describe. He would randomly suddenly start clawing or yanking at my dick while doing baby-talk, like a loud demeaning goo-goo-gaa-gaa thing that I never asked him to do and he wouldn't even do it during sex. the first time he did it was in bed early in the morning and it was out of nowhere and it really freaked me out. but then he "punished" me for "the manner in which I told him to stop" which was "in too mean a tone" and he gave me the silent treatment for a couple of days and made me feel like it was my fault. Then a couple of weeks later he did to me again, yanking my dick suddenly while doing baby-talk, while we in the car together and he was driving, not giving me a place to go and I was too afraid to react that time because what happened the last time. Understand that we had been in a committed relationship for three years once this had started happening, and we had been through a lot together, so in the midst of this, it was hard for me to see that it was legitimate sexual abuse. I had a therapist at the time who was not very helpful, but the therapist did encourage me to confront him about this as calmly and compassionately and articulately as possible (fuck therapists! am I right?). So the last time the guy did it to me was when I was telling him about the problem and he responds with a, "What? Like this?" and doing it again. He then said some of the worst things ever said to me, he said there was something wrong with me for loving him, he said that I always knew he was "evil" and the fact I was still there said something about me that i "need to explore", then creepily saying, "I'm proud of you so talking about it so calmly; can I get you a bowl of ice cream, as a reward?" I slept there one more night and then the next day I told him over the phone "no contact ever again" basically and used every last remaining ounce of my willpower to cut him out of, and keep him out of my life.
anyway this happened a little over two years ago and I'm still pretty fucked up about it. I took me a long time to admit to myself that this was sexual abuse and that, while I was never forcibly penetrated or anything like that, I have shown symptoms of rape trauma since this occurred. I can almost never get hard for other guys any more because a sense of terror in their presence, though I'm happy to get them off which I do well, so I'll still do that.
So sorry for unloading more than you probably wanted to know, but you did ask me to elaborate, and there is a moral to the story that you might need to hear: If something feels like sexual abuse, it probably is. This encounter you're talking about does sound like more than him simply getting carried away.