Which characteristic defines a semi-automatic rifle?

A semi-automatic rifle is defined by its ability to use the energy generated from firing a round to automatically load the next round into the chamber. This characteristic allows the shooter to fire a series of shots without needing to manually reload after each shot; instead, the rifle effectively cycles through the ammunition as each shot is fired. This design enhances the efficiency and speed of shooting, making it distinct from other types of firearms that require more manual operation, such as those that need a lever or other manual intervention to load the next bullet or are limited to a single bullet load.