This is what I found on the net .. LIKE THE ABOVE STATED .. get your head around something (informal) to be able to understand something. He's tried to explain the rules of the game dozens of times but I just can't get my head around them. (usually negative) HOPE IT HELPS

rodrod is correct. I would also add that sometimes a situation or a problem is so incomprehensible, so overwhelming not because you are not able to understand it, but because it is beyond what your expectations are that you "just can't get your head around it."

hello sash when you say I cannot get my head around it, it means that you are not able to understand something. You may have a particular problem which you just cannot figure and will then use the expression. eg. I struggled all night with the exercise but could not get my head around it.