Which word describes someone or something that is not secure?

The word "insecure" accurately describes someone or something that lacks security or confidence. When referring to a person, being insecure can mean they feel uncertain about themselves or their abilities, leading to feelings of doubt and vulnerability. Similarly, when something is described as insecure, it suggests that it is not firmly established or protected, which can lead to instability or risk. This captures the essence of the question, focusing on the absence of security.

In contrast, other terms such as "confident," "stable," and "solid" imply a sense of assurance, strength, or reliability, which directly opposes the meaning of insecure. Thus, "insecure" is the most fitting choice to convey the concept of lacking security.