Jousting is a sport, often as part of a tournament, in which two people on horses use lances with blunted tips to try to strike their opponent at high speed, preferably resulting in the opponent being knocked from their steed.
In 1367, Dr. Emmett Brown and his family arrived in England, and Doc Brown's wife Clara was kidnapped by the evil Lord Biffingham. Upon learning that Doc was Clara's husband, the Lord challenged him to a jousting match. When Doc's sons, Jules and Verne, attempted to make Doc win, their plan backfired. Afterword, Doc and his sons were sentenced to be beheaded.
Fortunately, at the last minute they were rescued by Clara, who escaped the Lord's castle in a makeshift hot air balloon that she had crafted. They flew out to Stonehenge, and returned in the DeLorean to Hill Valley in 1991.