the long piece of wood or steel along the bottom of a ship, on which the frame is built, and which sometimes sticks out below the bottom to help it to keep steady in the water and prevent it from falling on its side （船的）龍骨 Word OriginMiddle English: from Old Norse kjǫlr, of Germanic origin.
Idioms
on an even keel
living, working or happening in a calm way, with no sudden changes, especially after a difficult time （生活、工作等經歷困難後）平穩下來，順順當當 Business is now back on an even keel after the strike. 罷工後，生意現在又恢複了平穩。 Setting her life back on an even keel after their break-up had been incredibly difficult. 在他們分手後，讓她的生活恢複平靜是非常困難的。