Insecure (adjective)

1. Not confident or assured; uncertain and anxious about oneself; filled with self-doubt.
2. Not able to be relied on; uncertain.

Origin:

Late 16th century (in the sense "not secure"): from in- "not" + secure, on the pattern of latin insidiosus "treacherous".

Examples:

1. He felt insecure about his abilities.
2. She was insecure about her appearance.
3. The system was deemed insecure due to the lack of encryption.
4. The company was insecure about its future.
5. The investment was insecure and not recommended.