Silly/ˈsɪli/ Definition 1 of 5Pro Tip 1/2Lack of seriousness Use 'silly' to describe actions or decisions that are not taken seriously or done playfully. They wore silly hats to the party just for fun. Pro Tip 2/2Negative connotation 'Silly' can imply a mild reprimand or disappointment in someone's actions. Making a silly mistake like that could have been avoided.