Overlook it, it's not important; you're quite mistaken. This colloquial imperative is used in a variety of ways. For example, in Thanks so much for helpingForget it, it was nothing, it is a substitute for "don't mention it" or you're welcome; in Stop counting the changeforget it! it means "stop doing something unimportant" in You think assembling this swingset was easyforget it! it means "it was not at all easy"; and in Forget ityou'll never understand this theorem it means that the possibility of your understanding it is hopeless. [c. 1900]
Dictionary.com presents 366 FAQs, incorporating some of the frequently asked questions from the past with newer queries.