Definition
To act infectiously means to spread something, whether a disease, an emotion, or an idea, in a way that quickly affects others. It's similar to contagiously, but often emphasizes the impact on someone's mood or behavior. Think of it as catching a good mood from a friend. Unlike things that are easily ignored, infectious things tend to grab attention and spread quickly. It can refer to a catchy song, a viral meme, or even a shared sense of excitement. It is something hard to resist.