Image Macro
The (In)famous O RLY Owl

One of the most common pastimes available on the Internet. Take a fairly representative image of some kind, slap a redundant caption on it in a bold stark font, and upload it somewhere to share with people. It's as simple as that!

Most image macros are photographs of cats, called LOLCats, but they don't even have to be photographs. Captions are typically word replacements (called snowclones) of Internet memes, such as "Im in ur X, Ying ur Z", "I has a X", "X has a flavor", "redundant statement is redundant", and "invisible X".

The term comes from the Something Awful fora where certain keywords were replaced with funny pictures, or "images", by an automatic script, or "macro". The vast majority of lol* are not actually used that way anymore, but it's the term that most people know.