It means it does not work properly or it is damaged incorrectly built.
"Lemon" is an informal word for a product, particularly an automobile, that is defective.
The old man is defective about _____________.
It depends on what you mean. There is no specific name for a defective firearm other than to say it's defective.
defective or inadequate
Defective
The word cretin means a stupid or mentally defective person. Therefore, this word has negative connotation especially when used to refer to another person.
A rip-off is when you are cheated; for example, if you purchase a product and it is defective, or if you pay for a service and you do not receive what was advertised.
If you mean inadequate, it can mean defective, imperfect, incompetent or incomplete.
The opposite of the word perfect is bad
The mean is 0.1
Broken.
A defective product has a defect: "My phone is defective" "What defect does it have?" "The defect is that the screen is broken" To defect can also mean to switch sides e.g. from an army or a political party