fan service n. a feature, inside joke, or obscure reference included in entertainment primarily to please a core fan group, or a work of entertainment expressly created for that purpose; (hence) in anime and manga, visuals which include nude or semi-nude figures. (source: Double-Tongued Dictionary)
Further reading
The Great Passage is an anime about a young man who steps up to take over a project to edit a new dictionary, eventually becoming a full-fledged lexicographer. This is part of a complete episode.
Related
Centuries ago, monks who took a vow of silence developed their own hand signs, with hundreds of gestures, that are still in use today. Plus, how do speakers of different languages distinguish similar shades and tints of colors such as red, yellow...