Sorry about that, madtrapper.
I forgot that English is not your first language. The other thing an inline engine is called is a straight engine, as in straight six or straight eight, and flat is normally a synonym for straight, but not where automotive engine types are concerned. In an inline or straight configuration, the cylinders are all in a row, but in a flat engine the cylinders are arranged in opposed pairs.
Unfortunately, V-type aircraft engines are called inline engines to differentiate them from radial engines.
