Not to belittle anyone's religion, but I can't see how that can be the definition of hell.
I used to believe in God very strongly. I was even a Catholic priest for twelve years.
And I suffered. I experienced too much intolerance. I lived among extremely judgemental people. I have never seen anyone trying to control me all the time as much as I did during those twelve years.
It hurt. It was painful. Now, that was hell.
Then I embraced Buddhism. That was ten years ago. I did not really know much about it at the time, except that I was instictively drawn to it, and that I really liked the little I knew about it.
Naturally, having been a "professional religionist" (priest) before, I studied my new religion very intensively. I had not been aware of its nontheist nature. I gave it considerable thought before I embraced that part of Buddhism. But what liberation that was! No longer being under a constant supervision of God's whim was not hell. It was heaven. It was ecstasy. It was the kind of happiness I had never experienced before.
The blissful ecstasy lasted for a year or so. After that, it was gradually replaced by inner peace and balance.
No, an eternity apart from God is not hell. It is peace. At least for me - as I said I don't mean to belittle anyone else's beliefs.