Calling a "hockey stick graph" a
specialized scientific definition is a bit over the top, I'd say.
A "hockey stick" has two primary definitions:
something used to propel a ball or puck in hockey; and....wait for it....
something shaped like a hockey stick.
That the term is used to describe a statistical graph hardly qualifies it as a
specialized scientific definition (much to the chagrin of the lovers of the
Global Warming Hockey Stick Graph), any more than it qualifies as a
specialized artistic definition because it's a specific dance step in the Cha-cha-cha, or as a
specialized avionics definition because it's a procedure turn that is a standardized way of reversing course to get lined up on final approach during an instrument landing. The graph, dance step and procedure turn all are applications of the
something shaped like a hockey stick definition.
When the question of "Do you know what a "hockey stick" is?", gets asked, if the "hockey stick" in question is anything other than, uhm, you know, a
hockey stick, then it should be asked with the appropriate non-colloquial qualification as cl
arification for the principled purpose of clear communication (apt alliterations artful applied), as in; "Do you know what a 'hockey stick graph' is?", or "Do you know what a 'hockey stick procedure turn' is?", or "Do you know what a 'hockey stick dance step' is?"
When used to describe something
not a hockey stick, it's technically a
slang term (the jargon of a particular class or profession).
For an author to write as he speaks is just as reprehensible as the opposite fault, to speak as he writes; for this gives a pedantic effect to what he says, and at the same time makes him hardly intelligible. - Arthur Schopenhauer, author, philosopher, devout pessimist, and master of pedanticalness.
(The fact that the quote is an uncomfortably accurate description of me is irrelevant.) 
