Dictionary definition of defiance

It is often used to describe a refusal to comply with rules, laws, or commands, or a resistance to being controlled or dominated by others. For example, a person engaging in acts of defiance may refuse to follow orders from a superior, or disobey laws or regulations.
Defiance can also refer to the attitude or behavior of someone who is determined to stand up for what they believe in, or to assert their own autonomy, even in the face of opposition or adversity. It can also refer to an act of rebellion, or an act of standing up against something or someone that is deemed unjust or oppressive.

It implies a resistance or rejection of authority, control, or expectations and suggests that the person or the thing described as defiance is not willing to comply or submit. It implies a willingness to challenge the status quo or to stand up for what one believes in, even in the face of opposition or adversity.
Defiance can be seen as a positive or negative trait, depending on the context, as it can be used to stand up for oneself or for others, or to resist oppression, or on the other hand, it can be used to resist laws, rules or social norms for personal gain or for negative reasons.