Real Dictionary

hardly
If you say hardly had one thing happened when something else happened, you mean that the first event was followed immediately by the second.
You use hardly before a negative statement in order to emphasize that something is usually true or usually happens.
You use hardly to mean 'not' when you want to suggest that you are expecting your listener or reader to agree with your comment.
You use hardly to modify a statement when you want to emphasize that it is only a small amount or detail which makes it true, and that therefore it is best to consider the opposite statement as being true.
adverb: When you say you can hardly do something, you are emphasizing that it is very difficult for you to do it.
convention: You use 'hardly' to mean 'no', especially when you want to express surprise or annoyance at a statement that you disagree with.

hardly in American English
with effort or difficulty
adverb: only just; almost not; barely

hardly in British English
adverb: scarcely; barely