A more thorough explanation:

Definition: Improper is an adjective that means something is incorrect, unsuitable, or irregular. It can also refer to something that is fraudulent or otherwise wrongful.

• Wearing flip-flops to a job interview is improper attire.
• It is improper to cheat on a test.
• The company was fined for improper disposal of hazardous waste.

The first example illustrates how improper can mean unsuitable. Flip-flops are not appropriate for a job interview, so wearing them would be considered improper. The second example shows how improper can refer to something that is morally wrong. Cheating on a test is not only incorrect, but it is also dishonest and unethical. The third example demonstrates how improper can mean irregular or not following the rules. The company was fined for not following the proper procedures for disposing of hazardous waste.