A lie is the absolute truth that the government (or Caveman Joe) doesn't want you to know. Such as 'the cake,' which is actually a very delicious weapon of massive destructive goodness.
Other lies include things that Dan (the bartender at The Prancing SpiderKitty) may tell you when sending you on a DanQuest. For example, when Dan tells you, 'You can find this last monster (such as The Evil Chimera Chimental Chimrera Camera of Doom) in the jungles around New Pittsburgh,' he is lying.1)In fact it will be found in Cyberville404.2)3)4)5)
Anything Kassil says about changing time is a lie6). He's just a very skilled illusionist, if you look around Improbable Central and Common Ground, you'll find smoke machines and mirrors.7)8)9)