Well, I will tell you my definition. And since my definition is the only one that counts and the only correct one.....

A thru-hike is a hike that starts and stops at different locations. I did a thru-hike this last summer with my scouts. We were dropped off at one end, hiked 15 miles in two nights, and were picked up at the other end.

There are three main types of "hikes". A thru-hike, a loop-hike, and an out-an-back. A lollipop is a loop and an out-an-back. A "section hike" is a thru-hike, but the participant has a much larger goal in mind and just cuts it up into pieces.