(verb)
to cause a moving object to collide with something else, usually with some force and in a way that causes significant damage or destruction;
e.g. She was afraid she would crash her bicycle into the tree at the bottom of the hill.
(verb)
to move quickly and forcefully with a lot of noise, or to cause something to do this, or broadly, to cause something to make a lot of loud noise;
e.g. The children like to crash the pans together when playing. The thunder started to crash and it began to rain heavily.
(verb)
to attend an event without permission and/or without being invited;
e.g. He decided to crash their party and surprise them.
(noun)
a loud and sudden sound/noise caused by a collision, often involving significant damage or destruction;
e.g. The plate made a loud crash when it fell on the floor.
(noun)
a collision between a moving object and something else, usually involving great force and often resulting in significant damage/destruction;
e.g. There was a car crash on one of the main roads of the city, which is causing a serious traffic jam.