Speculative describes very risky and unproven ideas or chances. You might have great ideas about starting your own business but your plans are speculative until you earn money from them.
Speculative describes abstract ideas — usually with high risk — that often come with excitement and expectation too. A speculative investment could mean putting lots of cash into a business or real estate property hoping it will make money later. Anything speculative is based on prediction: whatever it is hasn't happened yet.