Vocabulary What does すいすい mean? すいすい means gliding smoothly (fish swimming, birds flying, work going without a hitch). Quick factsReadingすいすい すいすいすいすいTOPICSgliding smoothly (fish swimming, birds flying, work going without a hitch)Example sentences魚(さかな)が水(みず)の中(なか)をすいすいと泳(およ)いでいる。The fish are gliding smoothly through the water.