kiseo

1. (of taste) sour
   Ove jabuke su previše kisele. — These apples are too sour.
   Zimi jedemo mnogo kiselog kupusa. — In winter we eat a lot of sauerkraut.
2. (in chemistry) acidic
   Borovnice vole kiselo zemljište. — Blueberries like acidic soil.
   Kisele kiše uništavaju šume. — Acid rain destroys forests.
3. (of expression) sour; sullen
   Što si tako kiseo jutros? — Why are you so sour this morning?
   Samo se kiselo nasmejao. — He just gave a sour smile.

Kisela voda means sparkling mineral water, and kiselo mleko is a thick, set fermented milk product usually eaten with a spoon.