1. A thought that arises naturally and immediately without deliberation, planning, or conscious effort
Her spontaneous thought was to help the injured person immediately.
Seu pensamento espontâneo foi ajudar a pessoa ferida imediatamente.
2. An unplanned or instinctive mental reaction to a stimulus or situation
His spontaneous thought during the meeting revealed his true opinion.
Seu pensamento espontâneo durante a reunião revelou sua verdadeira opinião.