[v] talk over conjecturally, or review in an idle or casual way and with an element of doubt or without sufficient reason to reach a conclusion; "We were speculating whether the President had to resign after the scandal"
[v] reflect 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"
[v] to believe especially on uncertain or tentative grounds; "Scientists supposed that large dinosaurs lived in swamps."
[v] invest at a risk; "I bought this house not because I want to live in it but to sell it later at a good price, so I am speculating"
chew over, conjecture, contemplate, excogotate, hypothecate, hypothesise, hypothesize, job, meditate, mull, mull over, muse, ponder, reflect, ruminate, suppose, theorise, theorize, think over