I didn’t intent it to be specialist. It’s one of the most overused and misused terms in recent history. A fact that he seems to have understood along with the words.He means you used a specialist term - belonging to some branch of study - without explaining what it means. It's a bit like name-dropping, but academically more acceptable (at least on the surface).
Anyhow, you have the most comprehensive dictionary ever right in front of you.
Precise terms are invented because they are needed.