Removing (deleting) arrays

1

not elements in arrays but arrays themselves;

I am generating lots of arrays in a for loop again and again.

It it possible to delete these subArrays from the mainArray so that they dont exist any more?

var mainArray:Array = new Array();  
for (var i:int = 0; i< columns; i++) {
      var subArray:Array = new Array();            
      mainArray.push(subArray);
}

I forgot to write:
I am pushing movieClips into these subArray in this same for loop and later on, I am removing these movieClips from subArrays, but these subArrays (after being cleaned) still remain in mainArray, dont they?