Dingbat

North American (United States) "Dingbat" is what you can call someone when they do (harmless) space, careless, airheaded/silly things. It is not necessarily an insult, my mother would say "ya dingbat!" when I was spaceyy and tripped up with some task that was simple and easy and most likely routine. She used this word instead of instead of "you're silly" or instead of "you airhead!" It could be used as an insult I guess, but I've only used it in a "dark" manner when seriously discussing a person's actions and personality, when they have been implicated in something that did end up being a seriouse problem and/or mistake. In such a case, I would be using it to give context to their personality and actions. Up to the point of causing a danger or serious mistake, "dingbat" alone can be used to describe the person. If they did/do directly cause a harm, then that goes past being a dingbat. If they indirectly cause harm then they may or may not be within the dingbat range. If they tend to gossip or overall or share too much information and are not malicious, then dingbat can be an appropriate word. Whether or not the speaker is mildly to seriously annoyed with the person in question, dingbat is and is not the word to use. It really does vary but in most cases I havlve witnessed/been a part of, it is used to describe a dumb/spacey/careless person in situ. Or in general.