When you drop something, you let go of it and it falls. To drop a football is every receiver's nightmare. If you decide to drop your girlfriend or boyfriend, it will be their nightmare.
You might drop your dog's leash so she can sprint across the beach, or drop the heavy bags you've been carrying as soon as you walk in your front door. You can also drop to the ground yourself, to avoid being hit by your brother's remote control airplane. A drop is a fall, plummet, or plunge — literal, or figurative: "A drop in profits means we'll have to lay off some workers."