The word "non-serious" refers to something that lacks importance or gravity. In the realm of antonyms, there are several words that come to mind, including serious, consequential, grave, important, and significant. These words indicate that something has weight and should be considered with the attention and respect it deserves. Conversely, non-serious suggests something that does not require much thought or consideration. Other antonyms for non-serious are trivial, lighthearted, frivolous, unimportant, pointless, and insignificant. These words highlight the unimportance of something or suggest a lack of seriousness, indicating that it requires little attention or effort.