To drive or be driven against something; to strike against something; to clash; as, one heavy body knocks against another.

To strike or beat with something hard or heavy; to rap; as, to knock with a club; to knock on the door.

To strike with something hard or heavy; to move by striking; to drive (a thing) against something; as, to knock a ball with a bat; to knock the head against a post; to knock a lamp off the table.

To strike for admittance; to rap upon, as a door.

A blow; a stroke with something hard or heavy; a jar.

A stroke, as on a door for admittance; a rap.

a bad experience; "the school of hard knocks"

rap with the knuckles; "knock on the door"

To cast disparaging remarks about someone. Usually done behind his or her back also-rap