Open English Wordnet
Verbs
(v)speculate, theorize, theorise, conjecture, hypothesize, hypothesise, hypothecate, supposeto believe especially on uncertain or tentative grounds“Scientists supposed that large dinosaurs lived in swamps”
(v)chew over, think over, meditate, ponder, excogitate, contemplate, muse, reflect, mull, mull over, ruminate, speculatereflect deeply on a subject“I mulled over the events of the afternoon”, “philosophers have speculated on the question of God for thousands of years”, “The scientist must stop to observe and start to excogitate”