ADJECTIVE (1)

1. (of tempo) very fast;


ADVERB (2)

1. suddenly;
- Example: "Presto! begone! 'tis here again"- Swift

2. at a very fast tempo (faster than allegro);

The Collaborative International Dictionary of English v.0.48:

Presto \Pres"to\, adv. [It. or Sp. presto quick, quickly. See
   Prest, a.]
   1. Quickly; immediately; in haste; suddenly.
      [1913 Webster]

            Presto! begone! 'tis here again.      --Swift.
      [1913 Webster]

   2. (Mus.) Quickly; rapidly; -- a direction for a quick,
      lively movement or performance; quicker than allegro, or
      any rate of time except prestissimo.
      [1913 Webster]

WordNet (r) 3.0 (2006):

presto
    adv 1: suddenly; "Presto! begone! 'tis here again"- Swift
    2: at a very fast tempo (faster than allegro)
    adj 1: (of tempo) very fast

The Free On-line Dictionary of Computing (19 January 2023):

PRESTO

   A parallel language for shared-memory multiprocessors, built
   on top of C++ by Bershad et al, U Washington 1987.  PRESTO
   provides classes for threads and spinlocks as well as
   Mesa-style monitors and condition variables.

   (ftp://cs.washington.edu/pub/presto1.0.tar.Z).  E-mail:
   .

   ["PRESTO: A Kernel for Parallel Programming Environments",
   B.N. Bershad et al, U Wash CS TR, Jan 1987].