An impression that something might be the case
Hunch
Suspicion
Belief
Impression
Feeling
Notion
Opinion
Bosom
Heart
Intuit
He had an intuition that something had gone wrong
Instinctive knowing (without the use of rational processes)
Basic cognitive process
Sixth sense
Gnosis
Immediacy
Immediate apprehension
Insight
Inspiration
Intuitive feeling