Which word is defined as "the state of being unwilling or unable to believe something? "

incredulity
destitution
laved
voluptuously

The correct answer is: incredulity

Explanation:

So, incredulity is the state of being unwilling or unable to believe something.

e.g. Jane reacted to my question with concern and incredulity.

Destitution is the state of being without means, deprivation of something, or poverty.

e.g. The government should prevent families to fall into destitution by taking some radical measures.

Laved is the archaic form of the verb to lave, which means wash or bathe.

e.g. Hannah gently laved her wound with the cold water.

Voluptuously means full of something, characterized by luxury, pleasure or enjoyment.

e.g. He was eating a chocolate cake voluptuously.