expression, noun
total lie; complete fabrication
Emphasizes that something is entirely untrue, often used in accusatory or emphatic contexts.
彼の話は嘘の皮だった。
His story was a complete lie.
それは嘘の皮に決まっている。
That's obviously a total lie.
嘘 is the general word for 'lie'; 嘘の皮 is a stronger, more emphatic expression meaning 'a complete lie'.
大嘘 also means 'big lie', but 嘘の皮 carries a nuance of being a fabrication from start to finish, like a thin veneer of truth that is entirely false.
Literally 'skin of a lie', implying that even the surface is a lie; the exact origin is uncertain, but it is used to emphasize that something is completely false.