surprisal

Meanings

1. A surprise attack or ambush; a sudden or unexpected assault.
2. A sudden coming-upon someone or something unexpectedly or unawares.
3. A surprising event or occurrence.
4. The feeling caused by being surprised; surprise, shock, amazement.
5. 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.

Etymology

From surprise + -al. (information measure): Defined by Myron Tribus in the 1961 book Thermostatics and Thermodynamics.