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1.
combination of collide and clash

when two people fight and argue where words cannot describe how intense it is aside from using 'collash'
The arguing between John and Jane had intensified so much that they had collashed and caused a major scene in the mall.

That argument between John and Jane was so intense that it had become such a collash!
by SabrinaLightsN May 31, 2011
 
2.
It's when collapse is simply not enough and the crash is so epic you use a contraction of collapse, collision and crash: collash!
Wow brah, that crash was so epic! Did you see that collash?
- Yeah man, awesome!
by Funnybot6969 May 20, 2012