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., 1. pertaining to, of the nature of, or characterized by speculation, conjecture, or abstract reasoning. 2. theoretical, rather than practical. 3. given to speculation, as a person or the mind. 4. of or involving financial speculation. spec′u•la`tive•ness, n., Someone who has a speculative expression seems to be trying to guess something about a person or thing. His mother regarded him with a speculative eye. I caught her eyes on me speculatively. I imagined she was wondering about my relationship with Max., Speculative definition: pertaining to, of the nature of, or characterized by speculation, contemplation, conjecture, or abstract reasoning.. See examples of SPECULATIVE used in a sentence., Definition of speculative adjective in Oxford Advanced American Dictionary. Meaning, pronunciation, picture, example sentences, grammar, usage notes, synonyms and more., Speculative definition: Given to, characterized by, or based upon speculation or conjecture..