S.K.
Hi C.- does your husband usually play more rough and hands-on with her than you do? I know with my girls- they always play differently with me than with my husband! They roughhouse and fool around in a much more physical way than I do. This sometimes leads to them hitting him or kicking him- they think it's playing. It's like the kids don't quite understand and take it a bit too far sometimes.
Maybe she thinks she's playing and gets carried away.
If it's stemming from frustration and not from playtime- look at how he responds to her. Does he not hear her right away- or not respond as quickly as you do? Maybe she's biting him out of frustration or to get his attention.
You should both make sure you are on the same page as far as correcting the biting. Make sure he corrects her immediately. A stern and firm "teeth are not for biting" is a good way to address it. Immediately get down on her level- look her in the eye and say it very firmly and assertively. If they were playing he should stop and put her off to the side. Tell her that biting hurts Daddy and that he doesn't like it. If you react quickly and in the same way ever time it happens- it should stop quickly.
And remember- she really doesn't realize that it hurts as much as it does. She just knows she wants something.
Good luck,
S.