The molester who kept bothering passengers on the bus was arrested by the police.

molester 是由动词 molest（骚扰、性骚扰）加上名词后缀 -er 构成的名词，表示"实施骚扰行为的人"。molest 本身源自拉丁语，含有"干扰、烦扰"的意思。