A disagreement, parting of ways.
We had a fall out, couldn't come to terms and haven't talked since.
To come out of something by falling.
I opened the cupboard and a can fell out onto my foot.
To cease to be on friendly terms.
Dave and I fell out after a long argument.
To leave one's place in the current formation of ranks in order to take one's place in a new formation.
To leave one's current location to report for duty at a new location.
The company fell out for an artillery drill.
To pass out.
To turn out, happen.