Loli, considered an abbreviation for Lolita, is mostly used either for small characters with a youthful feminine appearance, or sometimes for characters dressed in lolita fashion. When abbreviated as just "loli", its most often to describe small female characters. Due to its nature, the majority of tagged works on pixiv are R-18 or R-18G.
The term "loli" refers to young looking female characters, The male equivalent is "shota".
Characteristics
Characters described as "loli" usually have some or all of the following traits:
Young age | Target characters frequently are given younger ages, often pre-teen. |
Small features | The target tends to have a small girlish physical features (short height, smaller breasts, a smaller waist) |
Youthful face | Some characters can have younger-looking facial proportions, giving the impression of a so-called "baby-face". |
"Loli" body type
For character design, there is value in creating distinction between male and female characters, even when there is minimal, if any, difference in reality.
For example, a real prepubescent girl's body shape is flat vertical line and featureless with a small torso or round protruding stomach. However, by adding more pronounced hips and tapering legs, a more feminine appeal can be created while retaining a cute appearance.
Lolicon and Pedophilia
The term lolicon (lolita complex) is often conflated with pedophilia (an attraction to children). And the term "loli" is often mistakenly treated as synonymous with "child", and its appeal is mistakenly viewed as being equivalent to pedophilia. Sometimes, the term "loli" (and the Japanese term it is transliterated from, ロリ) is used as an abbreviation for the term "lolicon", breeding further confusion.
The term "loli" is neither universally used with a sexual connotation, nor is it always associated with biological age. Sometimes, it is merely used as a term of endearment, and often, characters that are young looking but otherwise of age are also called lolis. Some characters, just like human people, are surprisingly young looking, by virtue of being e.g. shorter and flat chested, but have otherwise reasonable adult anatomy; these characters are often called "lolibaba" (ロリババア) or on Pixiv, old loli.