speculate (Verb) — To believe especially on uncertain or tentative grounds. ex. "Scientists speculated that large dinosaurs lived in swamps"
speculate (Verb) — 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. ex. "We were speculating whether the President had to resign after the scandal"
speculate (Verb) — Think deeply about a subject or question over a period of time. ex. "philosophers have speculated on the question of God for thousands of years"
speculate (Verb) — Invest at a risk. ex. "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"