A genre of popular furry character in Japan, literally being an abbreviation of chibi and kemono.
Not all chibi furries are chibikemo - chibikemo characters are designed with very small proportions even by chibi standards, usually fitting into the archetype of "TDM" (a mascot character who is 2-3 heads tall).
Chibikemo characters often have big eyes, are primarily animal-shaped despite their bipedal stance and anthropomorphic behavior (often being digitigrade), and are frequently fantasy creatures.
Chibi itself might not always apply, depending on the proportions of the character. Furry does not always have to be tagged, either, if the character is not the primary subject of the image but rather a mascot.
