"To flag the content" means to identify or bring attention to something in a piece of information, typically indicating that there is something noteworthy, concerning, or in need of review. Full definition
We appreciate your help in maintaining the quality of the site by utilizing the «report» button to flag content which does not adhere to our guidelines. (elitesingles.ie)
We also have a menu of options on the left side of the page, including Flag Content if we got something wrong. (town-court.com)
We review flagged content quickly, and remove inappropriate videos according to our policies.» (polygon.com)