Real Dictionary

bump
countable noun: A bump is a minor injury or swelling that you get if you bump into something or if something hits you.
countable noun: A bump is the action or the dull sound of two heavy objects hitting each other.
countable noun: If you have a bump while you are driving a car, you have a minor accident in which you hit something.
verb: If you bump into something or someone, you accidentally hit them while you are moving.

bump in American English
a light blow or jolt
to collide with a jolt
to hit or knock against with a jolt; collide lightly with
intransitive verb: to come in contact or collide with
transitive verb: to come more or less violently in contact with; collide with; strike

bump in British English
verb: to knock or strike with a jolt