My first thought was, were you being a bitch at the time?
I only ask because only the two of you know what led up to that insult, and what he actually meant by saying that. Is it a word which particularly upsets you?
I know that to some people, it's not the worst insult, and could have been used to describe behaviour/words from you which he found upsetting or spiteful. But only you can know if he was saying that just to be nasty, or if it was in response to something you said.
My DH has called me that on one or two occasions, during arguments, in the last 20 years, and it's not indicative of how he usually behaves towards me ( which is generally lovely and kind). It was more a demonstration of how horrible he thought I was being ( admittedly with some justification!).
People have different arguing styles, and none of us can know how you as a couple have dealt with arguments in the past.
If the relationship is one you want to continue, maybe you could make it clear how offended you are by that particular term, and that descending into name calling is something which upsets you. Presumably you don't do that to him. If he does it again, then you'll know where you stand.