Dumbslip means saying or doing something that is not correct.
Dumbslip is not really being a dumbshit, just an oversight in a detail that a person does that is a little embarrassing.
Is my dumbslip showing? I just gave my social security number to the cashier when she asked for my zip code.
I dumbsliped the spelling of my mother's maiden name, now my bank is giving me grief on my security questions.