expression, godan verb (-ru)
profit at someone else's expense; use others' resources for one's own gain
Proverbial expression meaning to take advantage of others' money, effort, or resources for personal benefit, often without risk to oneself. The image is of wrestling (相撲) using someone else's loincloth (ふんどし).
See also: 人のふんどしで相撲を取る (ひとのふんどしですもうをとる)
彼はいつも他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 at others' expense.
他人のふんどしで相撲を取るのはやめて、自分の力でやりなさい。
Stop using other people's resources for your own gain and do it with your own ability.