Itsy-bitsy means very, very small — but you say it in a playful, almost baby way, not as a serious size word. Adults use it when they want to sound cute or funny: an itsy-bitsy spider, an itsy-bitsy mistake, an itsy-bitsy bit of cake. You would not put it in a science report. It often sits with other singsong little words (teeny, weenie). A famous old pop song about an “itsy-bitsy teenie weenie yellow polka-dot bikini” is why a lot of people hear it and smile. You will also meet itty-bitty, which is the same joke in a slightly different shape.

丁點大、小小的（兒語、開玩笑）