A sponger is a person who lives off other people by continually taking advantage of their generosity. A sponge soaks up the water all around it. A sponger soaks up gifts, food and money without working.

Sponger（“寄生人”）指利用别人的慷慨、完全依赖别人的供给生活的人。之所以叫sponger，是因为sponge（海绵）会吸干它周围所有的水分，而这些“寄生人”就像海绵一样吸纳各种馈赠、食物和钱财，却不曾付出一分。

For example:

There were a bunch of spongers with cars and designer labels, eating in expensive restaurants all paid for by Daddy.

有那么一群“寄生人”，开着好车、穿着名牌、在高档餐馆就餐，而所有这一切都由他们的好爸爸买单。