From surprise + -al.
surprisal (countable and uncountable, plural surprisals)
- (obsolete, military) A surprise attack or ambush; a sudden or unexpected assault. [16th-19th c.]
- 1624, John Smith, Generall Historie, in Kupperman 1988, p. 146:
- Their chiefe attempts are by Stratagems, trecheries, or surprisals.
- (obsolete) A sudden coming-upon someone or something unexpectedly or unawares. [17th c.]
- How to secure the lady from surprisal.
- Because death is uncertain, let us prevent its surprisal.
- (obsolete) A surprising event or occurrence. [17th-19th c.]
- (obsolete) The feeling caused by being surprised; surprise, shock, amazement. [17th-19th c.]
- An information measure first defined by Myron Tribus in his 1961 book Thermostatics and Thermodynamics (D. Van Nostrand, New York) so that it is equal in bits to the base-2 log of 1 over the probability, with the result that e.g. the number of choices equals 2 to the number of bits.