surprisal

noun5

1. •
   An information measure as equal in bits (binary digits) to the base-2 log of 1 over the probability, with the result that the number of choices equals 2ⁿ where n is the number of bits.
2. •
   (no longer used) The feeling caused by being surprised; surprise, shock, amazement.
3. •
   (no longer used) A surprise attack or ambush; a sudden or unexpected assault.

   • Their chiefe attempts are by Stratagems, trecheries, or surprisals. — 1624
4. •
   (no longer used) A sudden coming-upon someone or something unexpectedly or unawares.

   • Because death is uncertain, let us prevent its surprisal. — 1678
5. •
   (no longer used) A surprising event or occurrence.