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