I think the definition you refer to in [1] is apt. "Things that exist or are used or enjoyed for only a short time." They are used or enjoyed for a short time

I think the definition you refer to in [1] is apt. "Things that exist or are used or enjoyed for only a short time." They are used or enjoyed for a short time because the cost or burden of doing so is extremely low. They are cheap, easily accessible, transportable, convenient, disposable. These are the attributes that make them ephemera, and that Fuller saw as ephemeralizing things.