noun
word game with inserted syllables
A language game where extra syllables (often し or similar) are inserted into words, e.g. やきもち becomes やしきしもしちし. Used for playful or secret communication.
子どもが入れ詞で遊んでいる。
The children are playing with the word game where extra syllables are inserted.
「やきもち」を入れ詞にすると「やしきしもしちし」になる。
When you apply the inserted-syllable word game to 'yakimochi', it becomes 'yashikishimoshichishi'.