That's my understanding, yeah. There's not a hard lìne of "must have below x density to be a void" but apparently around a tenth of the average density across the observable universe is typical. The largest known void is about three billion light years across and contains over 100,000 entire galaxies. I have absolutely no way to put measurement of that magnitude in to context, but "has 100,000 galaxies in it and is still considered to be notably empty" is wild to me