naduti

1. (of body, river; with se) to swell; to bloat
   Posle ručka mi se naduo stomak. — My stomach got bloated after lunch.
   Reka se nadula posle obilnih kiša. — The river swelled after heavy rain.
2. (+ acc.) to inflate; to puff out
   Dete je nadulo obraze i počelo da se smeje. — The child puffed out his cheeks and started laughing.
3. (with se) to become conceited; to get puffed up
   Čim je dobio unapređenje, naduo se kao paun. — As soon as he got promoted, he got all puffed up like a peacock.
4. colloq. (with se) to sulk; to get huffy
   Šta si se naduo, pa niko ti ništa nije rekao? — Why are you sulking? Nobody said anything to you.

For balloons and tyres, naduvati is more common in everyday speech.