Faulty (adjective)

Having a defect; not working properly.

Origin:

Late 16th century: from fault + -y.

Examples:

1. The car wouldn't start because the battery was faulty.
2. The laptop was returned to the store because it had a faulty keyboard.
3. The engineer found that the problem was caused by a faulty component in the circuit.
4. The company recalled all the products because they were found to be faulty.
5. The customers were unhappy because the product they received was faulty.