incompetent (adj.)

1610s, "insufficient," from French incompétent, from Late Latin incompetentem (nominative incompetens) "insufficient," from in- "not" (see in- (1)) + Latin competentem (see competent). Sense of "lacking qualification or ability" first recorded 1630s. The noun meaning "incompetent person" is from 1866. Related: Incompetently.

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Definitions of incompetent from WordNet
incompetent (adj.)
not meeting requirements;
Synonyms: incapable / unequal to
incompetent (adj.)
legally not qualified or sufficient;
incompetent witnesses
Synonyms: unqualified
incompetent (adj.)
not qualified or suited for a purpose;
the filming was hopeless incompetent
an incompetent secret service
incompetent (adj.)
showing lack of skill or aptitude;
Synonyms: bungling / clumsy / fumbling
incompetent (adj.)
not doing a good job;
incompetent at chess
Synonyms: unskilled
incompetent (n.)
someone who is not competent to take effective action;
Synonyms: incompetent person