BSD /B-S-D/ n. [abbreviation for `Berkeley Software Distribution'] a
   family of {{Unix}} versions for the {DEC} {VAX} and PDP-11 developed by
   Bill Joy and others at {Berzerkeley} starting around 1977, incorporating
   paged virtual memory, TCP/IP networking enhancements, and many other
   features. The BSD versions (4.1, 4.2, and 4.3) and the commercial
   versions derived from them (SunOS, ULTRIX, and Mt. Xinu) held the
   technical lead in the Unix world until AT&T's successful standardization
   efforts after about 1986; descendants including Free/Open/NetBSD, BSD/OS
   and MacOS X are still widely popular. Note that BSD versions going back
   to 2.9 are often referred to by their version numbers alone, without the
   BSD prefix. See {4.2}, and {{Unix}}.


Source: The Jargon File

BSD
     Berkeley System / Software Distribution (manufacturer, Unix, OS)
     
     
Source: Virtual Entity of Relevant Acronyms