TL;DR
Transient: keyword used in Java so that if the class it's encapsulated in is serialized, that it should be skipped (not saved)
In all fairness, this isn't really a hard concept
Oh, and it's used in plenty of other languages, too, e.g. C#. It's called transient because of the actual definition, which basically says that it doesn't last a very long time (when compared to non-transient variables in the class.)