fall over

Short definition from Wiktionary

Verb

1. 1
   To fall from an upright or standing position to a horizontal or prone position.
2. 2
   Of an argument, to fail to be valid.
3. 3
   Of a computer program or system, to crash.
4. 4
   To break down; to become inoperable.
5. 5
   To revolt or change allegiance.