An assertive person speaks their mind clearly and confidently.
When people describe someone as assertive, they usually mean that this person isn't afraid to express their opinions or needs. They say what's on their mind without being aggressive or rude. Being assertive is not about being bossy or dominating others; it's more like standing up for yourself in a respectful way. For example, if you're at work and someone asks you to do something that doesn't make sense, an assertive person would politely explain why they can't do it that way, but wouldn't just refuse without any reason.
Boldly self-assured; confident without being aggressive.
