What is the meaning of Bobber?

One who takes part in apple bobbing.

A buoyant device (frequently made of cork or hollow plastic) attached to a line so as to suspend the end of the line with the hook (and bait or lure) above the bottom.

A style of custom motorcycle with stripped-down bodywork and a shortened (or "bobbed") rear fender.

A person who rides a bobsleigh; a bobsleigher.

One who has a bob hairstyle.

Source: wiktionary.org