Conjecture means to guess or predict based on little or insufficient evidence.
Conjecture is a verb.
Synonyms: think , surmise, theorize, guess, fancy, imagine, infer, reckon, suppose, speculate.
The novel is nothing but pure conjecture; it is not based on any facts.
The judge urged the jury to avoid conjecturing and to decide the case on the basis of facts.
The gossip columnists are fond of conjecturing about famous hero.