conjecture

(noun) a hypothesis that has been formed by speculating or conjecturing (usually with little hard evidence). Synonyms: speculation. Examples: "Speculations about the outcome of the election." "He dismissed it as mere conjecture."

(noun) a message expressing an opinion based on incomplete evidence. Synonyms: guess, supposition, surmise, surmisal, speculation, hypothesis.

(noun) reasoning that involves the formation of conclusions from incomplete evidence.

(verb) to believe especially on uncertain or tentative grounds. Synonyms: speculate, theorize, theorise, hypothesize, hypothesise, hypothecate, suppose. Example: "Scientists supposed that large dinosaurs lived in swamps."