Billboarding is a term used to describe the advertising strategy of prominently displaying a brand or product in a way that is easily noticeable. However, there are several antonyms that can be used to describe the opposite of billboarding. One of these antonyms is subtlety, which refers to a more discreet and understated approach to advertising. Another antonym is modesty, which implies a more reserved and humble approach to advertising. Lastly, understatement can also be used as an antonym for billboarding, indicating a more subtle and restrained advertising style that focuses on the product or service's quality and usefulness rather than its flashy appearance.