Tosser (noun)

1. A person who throws something away carelessly; a wastrel.
2. A person who is considered to be stupid, incompetent or worthless.

Origin:

The origin of the word "tosser" is uncertain. it has been used as a slang term since the 20th century.

Examples:

1. He was called a tosser because he threw away perfectly good food.
2. He was a tosser because he didn't know how to fix the car.
3. The boss called him a tosser because he couldn't get the job done.
4. He was a tosser for not studying for the exam.
5. He was a tosser for not paying attention.