dry-as-dust

(as) dry as dust

1. Very dry. I followed the recipe exactly, and yet my cake is as dry as dust. I need to take out my contact lenses now because my eyes are just dry as dust.
2. Lacking any interesting or engaging elements; very boring. That lecture on polynomials almost put me to sleep—it was just dry as dust.
See also: dry, dust
Farlex Dictionary of Idioms.

dry-as-dust

mod. dull; lifeless. I can’t take another one of his dry-as-dust lectures.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • (as) dry as dust
  • dry as dust
  • dry (one's) eyes
  • high and dry
  • dry up
  • Dry up!
  • bone dry
  • be as dry as a bone
  • (as) dry as a bone
  • dry as a bone