Jargon
Jargon is specialist technical terminology used by those who work in a particular profession. Calling something jargon may have mild pejorative connotations. A more neutral phrase is term of art; especially in legal language, the implication is of terminology particular to one area of discussion or activity, which may in that context have a rather clear and well-defined application. That may be a more restricted or precise usage than is current in everyday speech.
For an account of jargon used in computer culture, in particular amongst hackers, see Jargon File.
See also