What is "pipedream"

Usage examples of "pipedream".

The science of biochemistry learned more in the next ten years than it had in the past seventy centuries, and the Oligarchy had sold the public on a pipedream: we were going to create a race of supermen that would blast the Setts to kingdom come.

When the case comes up he gets on his feet and says, 'Your Honour, my client, Miss Pearl Vambrace, wishes me to say that she does not consider herself libelled, and wants it understood that she has nothing to do with bringing this action, and that it's all a pipedream of her father's, who has got into a fantod about nothing very much.