sluz

1. (in the body) mucus; phlegm
   Ujutru imam mnogo sluzi u grlu. — In the morning I have a lot of phlegm in my throat.
   Nos mi je pun sluzi od prehlade. — My nose is full of mucus from the cold.
2. (of animals and plants) slime
   Puž je ostavio trag sluzi na stazi. — The snail left a trail of slime on the path.

The word is feminine: ova sluz, puno sluzi.