Opnieuw een diepgaand cybercultuurhistorische definitie op Wikipedia:
Lolcats, a compound of lol and cat, are photos of cats with humorous captions. They are a type of image macro, and are thus also referred to as cat macros. Lolcats are created for the purpose of sharing them with others on imageboards and other internet forums, especially on Saturdays (“Caturdays”).
Lolcat images consist of a photo, sometimes photoshopped, with words over the photo that are characteristically formatted in a sans serif font such as Impact or Arial Black. The captions generally act as speech balloons encompassing a comment from the cat or simple descriptions of the depicted scene, written in what has been variously called a kind of pidgin or baby talk. They are usually intentionally grammatically incorrect, with errors in spelling and syntax featuring “strangely-conjugated verbs.” Lolcats are similar to other animal-based image macros, such as the O RLY? owl and captioned pictures of walruses (lolruses), dogs, hamsters, birds, and rabbits.