Merriam-Webster's Collegiate® Dictionary, 11th Edition
CONJECTURE
I. noun see: jet
Date: 14th century
1. obsolete interpretation of omens, supposition ,
2. inference from defective or presumptive evidence, a conclusion deduced by surmise or guesswork, a proposition (as in mathematics) before it has been proved or disproved,
II. verb (-tured; conjecturing)
Date: 15th century
transitive verb to arrive at or deduce by conjecture ; guess , to make conjectures as to , intransitive verb to form conjectures, conjecturer noun