Speculative – Based on unproven theory and conjecture rather than knowledge
He believed that the spectre of a young relative (speculative) haunted the family home, but this was based on conjecture rather than knowledge.
Examples of speculative in a sentence
Theories on life and it's origins are highly speculative.
The murder mystery involved many speculative alibis that threw the audience off the scent.
The office block was built as a speculative venture.