oppai loli
Used when a child character has notably adult-sized breasts, but otherwise retains their child-like proportions. As a good rule of thumb, use the number of heads tall the character is to decide if they rank as an oppai_loli or not. Also note that oppai_loli isn't mutually exclusive to the explicit loli tag.
Similar to lolidonk, which is where a child-like character has a disproportionately large butt.
This tag implicates loli (learn more).