Informal/ɪnˈfɔːrml/ Definition 1 of 3Pro Tip 1/3Relaxed Interaction Used to show a situation is friendly and not serious. We're having an informal get-together this weekend. Pro Tip 2/3No Dress Code Indicates that you can wear comfortable, non-formal clothes. The invitation said the event was informal, so I wore jeans. Pro Tip 3/3Impromptu Events Refers to events that are not planned far in advance. Let's have an informal meeting to brainstorm ideas.