~ごっこ (playing pretend at X)

A noun-suffix attached to a noun to mean 'playing pretend at X,' 'X-game.' Always implies make-believe, never the real activity. Common in children's play vocabulary: 戦争ごっこ (playing war), お医者さんごっこ (playing doctor), 鬼ごっこ (tag, lit. demon-play).