Synonyms for Conjecture (same or very similar meaning)
WordNet sense 1 (a message expressing an opinion based on incomplete evidence):
guess, hypothesis, speculation, supposition, surmise, surmisalWordNet sense 2 (to believe especially on uncertain or tentative grounds):
hypothesize, speculate, suppose, theorize, hypothecate, hypothesise, theoriseFrom the ODE community, based on WordNetadd/edit