The Collaborative International Dictionary of English v.0.48:

Quantum \Quan"tum\, n.; pl. Quanta. [L., neuter of quantus how
   great, how much. See Quantity,]
   1. Quantity; amount. "Without authenticating . . . the
      quantum of the charges." --Burke.
      [1913 Webster]

   2. (Math.) A definite portion of a manifoldness, limited by a
      mark or by a boundary. --W. K. Clifford.
      [1913 Webster]

   Quantum meruit[L., as much as he merited] (Law), a count in
      an action grounded on a promise that the defendant would
      pay to the plaintiff for his service as much as he should
      deserve.

   Quantum sufficit, or Quantum suff. [L., as much suffices]
      (Med.), a sufficient quantity; -- abbreviated q. s. in
      pharmacy.

   Quantum valebat[L., as much at it was worth] (Law), a count
      in an action to recover of the defendant, for goods sold,
      as much as they were worth. --Blackstone.
      [1913 Webster]

WordNet (r) 3.0 (2006):

quantum
    n 1: a discrete amount of something that is analogous to the
         quantities in quantum theory
    2: (physics) the smallest discrete quantity of some physical
       property that a system can possess (according to quantum
       theory)

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

time slice
quantum
time quantum

    (Or "time quantum", "quantum") The period
   of time for which a process is allowed to run uninterrupted in
   a pre-emptive multitasking operating system.

   The scheduler is run once every time slice to choose the
   next process to run.  If the time slice is too short then the
   scheduler will consume too much processing time but if it is
   too long then processes may not be able to respond to external
   events quickly enough.

   (1998-11-06)