|Origin:||defeter 'to destroy', from Medieval Latin disfacere, from Latin facere 'to do'|
to win a victory over someone in a war, competition, game etc [= beat]:
They hoped to defeat the enemy at sea.
defeat somebody by something
We were defeated by 3 goals to 2.
if something defeats you, you cannot understand it and therefore cannot answer or deal with it [= beat]:
It was the last question on the paper that defeated me.
to make something fail
defeat the object/purpose (of the exercise)
Don't let your arms relax as that would defeat the object of the exercise.