Adjective speculative has 3 senses
- bad, insecure, risky, high-risk, speculative - not financially safe or secure; "a bad investment"; "high risk investments"; "anything that promises to pay too much can't help being risky"; "speculative business enterprises"
Antonym:  sound (indirect, via unsound)
 - notional, speculative - not based on fact or investigation; "a notional figure of cost helps in determining production costs"; "speculative knowledge"
Antonyms:  empirical, empiric (indirect, via theoretical)
 - inquisitive, speculative, questioning, wondering - showing curiosity; "if someone saw a man climbing a light post they might get inquisitive"; "raised a speculative eyebrow"
Antonym:  incurious (indirect, via curious)
 
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