pseudoprime n. a backgammon prime six consecutive occupied points
   with one point missing. this term is an esoteric pun derived from number
   theory: a number that passes a certain kind of "primality test" may be
   called a `pseudoprime' all primes pass any such test, but so do some
   composite numbers, and any number that passes several is, in some
   sense, almost certainly prime. the hacker backgammon usage stems from
   the idea that a pseudoprime is almost as good as a prime: it will do the
   same job unless you are unlucky.

pseudoprime
     
        a backgammon prime six consecutive occupied points with one
        point missing.  this term is an esoteric pun derived from a
        mathematical method that, rather than determining precisely
        whether a number is prime has no divisors, uses a
        statistical technique to decide whether the number is
        "probably" prime.  a number that passes this test is called a
        pseudoprime.  the hacker backgammon usage stems from the idea
        that a pseudoprime is almost as good as a prime: it does the
        job of a prime until proven otherwise, and that probably won't
        happen.
     
        jargon file
     
     
see also:
jargon file