diaper       
noun [ C ] US uk/ˈdaɪ.pər/ us/ˈdaɪ.pɚ/ (UK nappy)
 尿布
a square of thick soft paper or cloth that is fastened around a baby's bottom and between its legs to absorb its urine and solid waste
  disposable/reusable diapers 一次性/可重复使用的尿布 
 diaper cream 护臀霜 
 She was changing the baby's diaper. 她在给婴儿换尿布。 
 I knew William when he was still in diapers (= when he was a baby). 威廉还穿尿布的时候我就认识他了。