I just encountered this term used by a German person who couldn't find the translation, but it turns out that it does *not* mean palindrome, but rather a specific subtype of palindromic number known as a repdigit. That is, all digits in the number must be the same: 11111, 222, 888888, etc.
There are 55 repdigit numbers between zero and a million (counting zero), although the numbers 0-9 usually aren't counted, making it 45.