surprisal

Meaning

Noun

• A surprise attack or ambush; a sudden or unexpected assault.
• A sudden coming-upon someone or something unexpectedly or unawares.
• A surprising event or occurrence.
• The feeling caused by being surprised; surprise, shock, amazement.
• An information measure as equal in bits 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.

Origin

• From surprise + -al.
• Defined by Myron Tribus in the 1961 book Thermostatics and Thermodynamics.