Drone has two main meanings:

1. A flying aircraft with no pilot inside, controlled remotely by a person on the ground or programmed to fly on its own. Some drones are tiny toys you can fly in your backyard with a remote control. Others are massive military aircraft that can fly across oceans. Scientists use drones to study volcanoes, farmers use them to monitor crops, and photographers use them to capture amazing aerial shots that would be impossible from the ground. A delivery drone that might someday bring a package to your door would follow preprogrammed instructions combined with real-time adjustments.
2. A low, continuous humming sound. A bee makes a droning buzz as it moves from flower to flower. Someone speaking in a boring, unchanging voice might drone on and on about a topic, causing everyone to lose interest. When a teacher drones through a lecture without varying their tone, students' minds start to wander. The word suggests something monotonous that goes on longer than you'd like, whether it's a sound or a way of speaking.