1.Definition: legally not qualified or sufficient

"Incompetent witnesses"

Related Adjective(s):unqualified

2.Definition: not doing a good job

"Incompetent at chess"

Related Adjective(s):unskilled

3.Definition: not meeting requirements

Related Adjective(s):incapable

4.Definition: not qualified or suited for a purpose

"An incompetent secret service", "The filming was hopeless incompetent"

5.Definition: showing lack of skill or aptitude

Related Adjective(s):bungling, clumsy, fumbling