This is the 2742nd most frequent Swedish word.
underligt
Strange or unusual.
Here, 'underligt' means 'strange' or 'odd' and is used to describe an unusual behavior.
Det är underligt att han inte sa hej när han såg oss.
It is strange that he did not say hello when he saw us.
In this context, 'underligt' describes the peculiar shape of the stones, acting as an adverb.
Jag hittade underligt formade stenar på strandpromenaden.
I found oddly-shaped stones on the beach promenade.
The word 'underligt' is used to depict an eerie or unusual aspect of someone's look.