In the broadest possible sense, fencing is the practice of armed combat involving cutting, stabbing or bludgeoning weapons directly manipulated by hand, rather than shot or thrown - swords, knives, pikes, bayonets, batons, clubs etc. In contemporary common usage, fencing tends to refer specifiaclly to European schools of swordsmanship and to the modern Olympic sport which has evolved out of them.
Also, stage-fencing - the practice of representing sword-fights on stage or screen; academic fencing - a form of ritualised combat practiced by some German student fraternities.