noun
tag; chasing game
A children's game of chasing and catching one another; equivalent to 'tag'.
子供たちが公園で追いかけっこをしている。
The children are playing tag in the park.
追いかけっこしよう！
Let's play tag!
鬼ごっこ is a specific type of tag with an 'it' (鬼), while 追いかけっこ is a more general term for chasing games.
From 追いかける (to chase) + っこ (suffix indicating mutual action).