A dingbat is an ornament or spacer used in typesetting, sometimes more formally known as a "printer's ornament". The term supposedly originated as onomatopoeia in old style metal-type print shops, where extra space around text or illustrations would be filled by "ding"ing an ornament into the space then "bat"ing tight to be ready for inking .
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Noun 1. a silly empty-headed person; "you would be a dingbat even to try it"; "yet here he was with an upper class dingbat who just happened to be married to his sister" (hypernym) simpleton, simple