I would define dystopia as a futuristic imagined world in which a tyrant or tyrannical ruling class instills fear in their subjects who have no sense of privacy, property, or freedom and above all a feeling of desolate hopelessness amongst themselves.
The reason I would use this definition is because I feel as if it captures the key elements that contribute to the nightmarish nature of what a dystopia is imagined or thought to be. For example, the reason I used the term tyrannical rule is because dystopias are often characterized by an oppressive governance that exercises extreme excessive control over the citizens. It is the extremeness and excessiveness that makes it tyrannical and also what instills the fear mentioned as well. This fear is used as a Tool by those in power to maintain control and serve as a means to suppress dissent and discourage resistance. I used the absence or loss of privacy and property to encapsulate the loss of basic rights and freedom those in dystopias usually face. It is this loss of rights that can create a sense of vulnerability and powerlessness. This leads to a group of individuals who have desolate hopelessness as they are deprived of agency and basic human connections, reinforcing the dystopian atmosphere.
The reason I used the term futuristic is because most dystopias appear to depict the consequences of mismanaged technological advancements coupled with unchecked power or totalitarian/tyrannical regimes. In summary, the reason I would use this definition to define dystopia is because it captures the core elements that contribute to the grim and unsettling nature of dystopian worlds that attempt to explore the darker aspects of human nature, and repercussions of going down specific societal paths or maintaining and expanding upon certain societal norms and or the misapplication of progress being made in science and technology.