From the term gateway drug but referring to beer. A beer that acts as a gateway to drinking tastier, more delicious craft beers. A beer you drink because you truly enjoy the flavor, not just as a reason to get schnockered.
It was drinking Old Spotted Sow that finally turned me away from factory made lite lagers. It was my gateway beer.
I started out drinking fool fizz as a gateway beer. After that I moved on to more hoppy, malty beers. Now I can't drink anything else.