speculate

verb

1. to believe especially on uncertain or tentative grounds"Scientists supposed that large dinosaurs lived in swamps"
2. 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"
3. reflect deeply on a subject"I mulled over the events of the afternoon"
4. 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"