Hogwash is complete nonsense, lies, or ridiculous actions. If an advertisement claims that taking one vitamin pill a day will make you ten times stronger, that's hogwash.
The informal hogwash is perfect for talking about falsehoods and foolishness. Your little brother may insist that his lemonade stand will make him a millionaire this summer, but you know that's hogwash. And many politicians give long speeches that seem, in retrospect, to be nothing but hogwash. The word has seen a dramatic evolution, from the fifteenth century "slops fed to pigs," to "cheap liquor" in the 1700s, to "inferior writing" towards the end of the eighteenth century.