Correct Answer: Ambiguous

Solution : The fourth option is correct.

Ambiguous means having more than one possible meaning or interpretation, which is unclear. This is the closest synonym to equivocal, as it also denotes something that is not clear or straightforward in meaning.
The meanings of the other options are as follows:

• Definite: Clear, certain, or unmistakable.
• Secure: Safe, protected, or certain.
• Insecure: Not safe, uncertain, or lacking confidence.

Therefore, the correct answer is ambiguous.