expression, godan verb (-ru)
profit at someone else's expense; use others' resources for one's own gain
Idiomatic expression literally meaning 'to wrestle using someone else's loincloth'. It describes benefiting from or taking advantage of other people's efforts, money, or resources without contributing oneself.
See also: 他人のふんどしで相撲を取る (たにんのふんどしですもうをとる)
彼はいつも人のふんどしで相撲を取るようなやり方をする。
He always does things in a way that profits from others' efforts.
人のふんどしで相撲を取るのはやめて、自分で努力しなさい。
Stop taking advantage of others and make your own effort.