Sheltron

A sheltron (also sceld-trome, schiltrom or shiltron) is a compact body of troops forming a battle array, shield wall or phalanx.

While Tolkien wrote that the Orcs were already demoralized before Gandalf arrived, the film encounter is somewhat more dramatic with the Orcs forming up an organized sheltron against the charging Rohirrim horseman but at last minute the Orcs' line falters after they are dazzled by sunlight.