This is the 662nd most frequent Dutch word.
erger
"Worse."
Here, 'erger' is used as a comparative adjective, denoting a deteriorating condition.
De situatie is nog erger geworden.
The situation has worsened.
In this sentence, 'erger' acts as a comparative adjective in an idiomatic expression implying that a certain aspect is comparatively worse.
Wat erger is, hij heeft helemaal niets gezegd.
What is worse, he hasn’t said anything at all.
Here, 'erger' is part of the reflexive verb 'zich ergeren,' meaning to be annoyed or irritated.