List 21

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Across
  1. 1. underground train or its path or system
  2. 2. relating the layer just beneath the skin
  3. 3. an expression that uses exaggeration
  4. 4. the best, highest, or greatest
  5. 5. difficult to detect
  6. 6. abnormally or extremely busy or engaged
  7. 7. not existing within the physical order
  8. 8. severely low body temperature
Down
  1. 1. to put completely under water
  2. 4. a ship that operates underwater