an advertisement that is used to make people interested in a product, but that does not give very much information about the product, so that people will pay attention to more advertisements later 前导广告，预热广告〔引起人们对产品的兴趣，但不会给予过多信息的广告，以此吸引人们注意其后推出的更多广告〕
From Longman Business Dictionary
teaser adˈteaser adMARKETING
an advertisement that is used to get the public interested by giving very little information about the product. The purpose is to get attention for the full ADVERTISING CAMPAIGN that follows