Basically a sub for people, posts, links, etc. that took the easy way out and commented with a sub link that has become a low-effort meme. Examples include; r/theydidthemath, r/nocontext and r/jesuschristreddit. Not limited to links, other examples of "shooting fish in a barrel" include "This guy *blanks*", "Roll Tide", "NEXT!" and "And everybody clapped"