Different contest judges have called my manuscript, OUT OF THE SHADOWS, a thriller and some said it's a suspense novel. I don't think it's either. I believe it's a spy/mercenary romance. Anyway, I decided to look up the meanings.
Wow! There are a lot of opinions out there but truthfully several missed the mark. Most don't even really answer the question. So here's my opinion for whatever little it's worth.
Thriller: A situation that becomes bad, worse and then terrible. It usually grows from one person who wants something. He/she is obsessed and unreasonable. The reader often knows the person who has gone crazy. He/she may start small but their desire for whatever escalates. One website mentioned usually a thriller crosses borders or statelines with a larger than life feel to it.
Suspense: Normally the reader doesn't know who's the killer. The bad guy (or gal) can be a serial killer or just after one person in the story. I believe a suspense is more centered on a small area or group. A mystery is often woven through the story.
Okay. Discuss amongst yourself.