Definitions for uncausedʌnˈkɔzd
Random House Webster's College Dictionary
without an antecedent cause.
Origin of uncaused:
causeless, fortuitous, uncaused(adj)
having no cause or apparent cause
"a causeless miracle"; "fortuitous encounters--strange accidents of fortune"; "we cannot regard artistic invention as...uncaused and unrelated to the times"
That which happens spontaneously, unintended and uninitiated.
Since all things must come from something that causes them the uncaused cause is that one thing that began the chain of existance, often identified as God.
having no antecedent cause; uncreated; self-existent; eternal