Definition of speculate

• to believe especially on uncertain or tentative grounds; "Scientists supposed that large dinosaurs lived in swamps"
• 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"
• 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"