nakupiti

1. (+ acc. or gen.) to accumulate; to amass
   Za godinu dana nakupio je gomilu starih stvari. — In a year he accumulated a pile of old stuff.
   Nakupila sam dosta iskustva radeći u kafiću. — I gained a lot of experience working in a café.
2. (nakupiti se) to build up; to pile up
   Na polici se nakupilo mnogo prašine. — A lot of dust has built up on the shelf.
   U njemu se nakupilo mnogo besa. — A lot of anger had built up inside him.

Often used with the genitive of quantity: nakupiti novca, nakupilo se vode.