speculate in WordNet English dictionary

1. 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"
   chew over  think over  meditate  ponder  excogitate  contemplate  muse  reflect  mull  mull over  ruminate  speculate 
   
2. to believe especially on uncertain or tentative grounds
   "Scientists supposed that large dinosaurs lived in swamps"
   speculate  theorize  theorise  conjecture  hypothesize  hypothesise  hypothecate  suppose 
   
3. 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"
   speculate  job 
   
4. 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"
   speculate