A dingle is a small, deep, wooded valley or a deep, narrow cleft between hills.
In Treasure Island, Mr. Dance, a tax collector, is in hot pursuit of a pirate crew:
In the meantime [Dance] rode on, as fast as he could, to Kitt's Hole; but his men had to dismount and grope down the dingle, leading, and sometimes supporting, their horses, and in continual fear of ambushes . . .