A word similar to childish, used to define someone who acts like a kid in most cases. However it does not have to mean immature but simply acting like someone of a young age, or showing something that relates to a kid.
Examples:
My girlfriend wanted me to go to the playground with her then go back to her place and eat cookies and milk to me that just seems kiddish.
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi
May I have an order of regular degular buttermilk pancakes? Without all the added jazz? Hold the blueberry smiley face, strawberry glaze, chocolate chips and whipped cream.