A garbled message makes no sense. If you get a bad phone connection, your friend's message might sound garbled. Or, if you have rewritten the same sentence numerous times, its message might also be garbled.
When you were young you may have played the game telephone, where one student thinks up a line, whispers it to his neighbor, who whispers it to his neighbor, and so on, down the line. At the end, the last person to receive the message shouts it out; it usually has nothing to do with what the first person said: it has been garbled along the way. Most of the change is accidental, the price of being human and imperfect — you hear "dope" rather than "hope." Besides messages, facts can get garbled — remember the history test where you wrote 1960 instead of 1860?