When people say “they're engaged,” the phrase “to be married” 'is understood'. [=“they're engaged” is understood to mean “they're engaged to be married”]
We still don't fully 'understand' the causes of the disease. = The causes of the disease are still not fully 'understood'.
He believed it 'was understood' [=believed that everyone had agreed] that he would be paid for the work.
(..) 'T Do fast, and free. A kite blocks. Flowers. This is blue leader, we have roses understanding ... At degrees, and wait. Rozen. - Degrees, understood. We go out. Stay at a distance, guy. He has a small setback. That is now a collector nectar. Do you ever sometimes pollination closely? - No, sir. (..)2007 Bee Movie