What is "to bob at an apple"

Bob \Bob\, v. i.

1. To have a short, jerking motion; to play to and fro, or up and down; to play loosely against anything. ``Bobbing and courtesying.''
   --Thackeray.

2. To angle with a bob. See Bob, n., 2 &

3. He ne'er had learned the art to bob For anything but eels.
   --Saxe.

   To bob at an apple, cherry, etc. to attempt to bite or seize with the mouth an apple, cherry, or other round fruit, while it is swinging from a string or floating in a tug of water. [1913 Webster] ||