Definition
This idiom suggests that it is often best to say very little about a problematic situation, as discussing it further can make it worse; the less said about a delicate matter, the sooner it will be forgotten.
It's best we keep quiet about the argument; least said soonest mended, after all.
I think we should avoid discussing this mistake further. Least said soonest mended, right?
They didn't say much about the failed project; it seems they believe least said soonest mended.