Maybe this is a good definition.
Proof beyond a reasonable doubt, therefore, is proof of such a convincing character that you would be willing to rely and act upon it without hesitation in the most important of your own affairs. However, it does not mean an absolute certainty.
That is the definition that most states used to template the review of their defintion of proof beyond a reasonable doubt after the Supreme Court's ruling in Victor v. Nebraska.
I have posted elsewhere that in performing this review and rewrite, the template that most, if not all, states used to create their new model for reasonable doubt was: "The level of certainty a juror must have to find a defendant guilty of a crime. A real doubt, based upon reason and common sense after careful and impartial consideration of all the evidence, or lack of evidence, in a case. Proof beyond a reasonable doubt, therefore, is proof of such a convincing character that you would be willing to rely and act upon it without hesitation in the most important of your own affairs. However, it does not mean an absolute certainty."
While no state ended up with the above as their new model definition for reasonable doubt, states did freely extract from it. But, basically, across our fifty states, there are now over forty different definitions of reasonable doubt.
Still, if you look at the above template definition, it comes across very clearly. So ask yourself this question: within the most important of your own affairs, what would constitute such a convincing character that you would be willing to act upon it without hesitation in the most important of your affairs? For example, would you drop your little child off in a situation where you thought there was 1 in a 100 chance that they could suffer serious harm?
Of course, most people can relate to this and intuitively recognize that it is unlikely they would not drop their little child off if they were of the mind that those odds existed.
At the very least, this kind of mental exercise allows people to position the definition of reasonable doubt to their own personal affairs, and it also allows people to gauge (calibrate) how high the "proof beyond a reasonable doubt" standard truly is.
Now, I do not know about you, but if the odds were 1 out of a 100 that my child might suffer serious harm (a 99% degree of certainty that they would not suffer harm), not only would I not drop my child off, I would not drop my dog off either!!