spl

   [abbrev,  from  Set  Priority Level] The way traditional Unix kernels
   implement  mutual exclusion by running code at high interrupt levels.
   Used  in  jargon  to  describe  the  act  of  tuning in or tuning out
   ordinary  communication.  Classically,  spl  levels  run from 1 to 7;
   "Fred's at spl 6 today" would mean that he is very hard to interrupt.
   "Wait  till  I finish this; I'll spl down then." See also {interrupts
   locked out}.

[glossary]
[Reference(s) to this entry by made by: {interrupts locked out}{Nightmare File System}]