He's known for freeloading at his friends' places without ever inviting them back.

freeloading 是动词 freeload 的现在分词形式。freeload 由 free（免费的）和 load（装载、负担）组成，字面意思是"免费装载"，引申为"占便宜、蹭吃蹭喝"的行为。freeloading 指"蹭吃蹭住、占别人便宜"的行为。