a small stick with a small amount of cotton wool (= soft, white material) on each end that is used for cleaning the skin, putting on make-up, etc.

She uses a cotton swab to blur the eyeliner a little. 她用棉签稍微晕染了一下眼线。

They take a small tissue sample from the inside of the mouth with a cotton swab. 他们用棉签从口腔内部取出一小块组织样本。