dubious
The definition for dubious is "Questionable." Used in a sentence: Karl found Kevin's claim that he was sick dubious, as he had just seen him playing football.
extant
The definition for extant is "Currently existing." Used in a sentence: Some consider Clint Eastwood the greatest extant American director.
extenuating
The definition for extenuating is "Partially excusing." Used in a sentence: The extenuating circumstance of Calvin's illness caused the teacher to excuse his lateness.
incisive
The definition for incisive is "Impressively direct and decisive." Used in a sentence: Samir's incisive leadership made him the natural choice for president of the company.
incongruous
The definition for incongruous is "Not harmonious, incompatible." Used in a sentence: Sadie's cowboy hat was incongruous with her black cocktail dress.