Definition
Acting childishly means behaving in a way that's immature or like a young child. It often involves being silly, throwing tantrums, or being overly dramatic. It's the opposite of behaving maturely or responsibly. For instance, arguing over a video game controller is acting childishly, whereas taking turns is mature. Childishly implies a lack of self-control and consideration for others. Think of it as acting like a toddler when you're old enough to know better.