knock noun
1 firm sharp sound
ADJ. loud, sharp | gentle, light | determined | timid
VERB + KNOCK hear | answer She hurried to answer the knock at the door.
PHRASES a knock at/on the door There was a loud knock at the door.
2 sharp blow from sth
ADJ. hard, nasty, severe (figurative) the hard knocks of life | minor
VERB + KNOCK get, have, take You've had a nasty knock on the head. (figurative) Their pride took quite a knock when they lost 5?0. | give sb/sth
PREP. ~ on