The table is unstable because one leg is shorter than the others.这桌子一条腿比其它的腿短，所以不平稳。That wheel is off balance.那个轮子不平稳。The flight was very bumpy.飞行很不平稳。The aircraft bumped along erratically without gathering anything like sufficient speed.飞机忽上忽下，飞行很不平稳，根本未达到应有的速度。