The man was staring at her lasciviously, which made her feel extremely uneasy.

lasciviously 是副词，由形容词 lascivious（好色的、淫荡的）加上副词后缀 -ly 构成。lascivious 源自拉丁语 lascivia，意为"放荡、淫荡"。 lasciviously 形容一种带有性暗示或淫荡意味的注视方式，通常让人感到不适或被冒犯。