Speculative (adjective)

1. Involving, based on, or constituting speculation.
2. Not having been proven or confirmed; hypothetical.

Origin:

Late middle english: from old french speculatif, -ive or medieval latin speculativus, from latin speculari "consider, gaze at".

Examples:

1. He made a speculative investment in the stock market.
2. The theory is still speculative and needs more research.
3. The book is a work of speculative fiction.
4. The company is engaged in speculative building.
5. He made a speculative proposal for a new project.