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Acronym, originating in the early 20th century, and popularized by Robert Heinlein's novel, The Moon is a Harsh Mistress.



  1. (idiomatic) There ain't no such thing as a free lunch; something advertised as being "free" will invariably have hidden costs.
    • 1966, Robert Heinlein, The Moon Is A Harsh Mistress,
      "Gospodin," he said presently, "you used an odd word earlier--odd to me, I mean..."
      "Oh, 'tanstaafl.' Means 'There ain't no such thing as a free lunch.' And isn't," I added, pointing to a FREE LUNCH sign across room, "or these drinks would cost half as much. Was reminding her that anything free costs twice as much in long run or turns out worthless."
    • 1985, Lance Parkin, The Infinity Doctors, page 229,
      'Tanstaafl. There ain't no such thing as a free lunch. We both know that I was brought here for a reason. If we could get down to business.'