It is clear, compelling, and easy to grasp. The goal in a good BHAG is obvious, no matter how you phrase it.
for example, Philip Morris's BHAG, set in the 1950s-to knock off R.J.Reynolds as the number one tobacco company in the world - didn't leave much room for confusion.
I can this the "Mount Everest standard "
The goal to climb Mount Everest can be said as "Climb the most famous mountain in the world" or "Climb the biggest mountain in the world