Definition of ratiocinate in US English:

ratiocinate

verb

[no object]formal
  • Form judgments by a process of logic; reason.

    • ‘His father, Alan Fry, was written up as the villain in these early times; an inventor whose ‘infuriatingly, cold, precise ratiocinating engine of a brain fuelled by a wholly egocentric passion.’’
    • ‘If the candidate seems prepared to ratiocinate every policy question rather than apply values to its solution, that candidate will lose.’
    • ‘Man is said, for instance, to be the ‘rational animal,’ but you won't find much ratiocinating among fetuses.’
    • ‘Almost definitely two, actually, since she knew there were three new arrivals, and of course, she had already met one, she ratiocinated.’
    think rationally, think logically, think straight, use one's mind, use one's common sense, use one's head, use one's brain, think things through, cogitate
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Origin

Mid 17th century: from Latin ratiocinat- ‘deliberated, calculated’, from the verb ratiocinari, from ratio (see ratio).

Pronunciation