Fencing can have 2 definitions: Those wooden/vinyl posts around your property, or fighting with long weapons (generally swords).
From the Online Etymology dictionary:
fence (v.)
"fight with swords,"...
Fencing is a sport in which two opponents wield swords against one another while heavily protected. Their goal is to touch or poke the other person with their blade.
Fencing is a sport of three different types, or styles of fighting: Saber, Epee, and Foil. These three different styles have different target areas, rules, and ways of getting a touch (a point)....