Definition - What does Interstitial Ad mean?
An interstitial ad is an online ad that is dynamically displayed at natural transition points in an interface design. It is commonly displayed in full screen or in large size that can obstruct most of the viewer's screen. Typically, users have to navigate past these large ads to continue on a particular online activity.
Techopedia explains Interstitial Ad
One of the most primitive forms of interstitial ads was the “pop-up ad” used in the early days of the Internet. Computer users would see large pop-up ads suddenly obstructing the screen during surfing. Because these pop-ups were in separate windows, it was relatively easy to click out of them, unless there were too many of them (as sometimes happened). Pop-up blockers were thus developed to address this issue.
Now, the use of interstitial ads has extended to the mobile world as well. Users might see these ads pop up as they play a game, read an article or navigate a Web page.