conjecture

noun

1. (countable, formal, uncountable)A statement or an idea which is unproven, but is thought to be true; a guess.

   “I explained it, but it is pure conjecture whether he understood, or not.”

2. (countable, formal, uncountable)A supposition based upon incomplete evidence; a hypothesis.

   “The physicist used his conjecture about subatomic particles to design an experiment.”

3. (countable, uncountable)A statement likely to be true based on available evidence, but which has not been formally proven.
4. (countable, obsolete, uncountable)Interpretation of signs and omens.

verb

1. (formal, intransitive)To guess; to venture an unproven idea.

   “I do not know if it is true; I am simply conjecturing here.”

   “What could have been done by such a machine downhill can only be conjectured, for the maximum speed was restricted rigidly to 80 m.p.h.”

2. (transitive)To infer on slight evidence; to guess at.

   “February 22, 1685, Robert South, All Contingences under the Direction of God's Providence (sermon preached at Westminster Abbey)”

   “"Most likely he who is the shorter of the two;—no! he goes in the first, and is, of course, the eldest; but we have no time for conjecturing now." Human reason can then, at the best, but conjecture what will be.”