Falling or dropping very quickly from a high place.
Plummeting usually makes people feel worried or scared. It can also make people feel surprised.
Examples:
The bird is plummeting from the sky.
The price of the toy is plummeting.
She is plummeting down the stairs.
The number of people at the party is plummeting.
The spaceship is plummeting to the ground.
The apple is plummeting from the tree!