I've heard cowboy used an adjective to describe something (most likely
something poorly shimmed together on the road, just good enough to
work).
Many nouns can be used attributively as modifiers, as in cowboy boots, meaning typical of, or referring to, a cowboy or cowboy style.
It appears, however, that cowboy as a modifier can also mean jury-rigged, improvised, expedient, suboptimal, etc. as illustrated in the following examples of cowboy modifying solution, IT, and engineering. (I'm not sure how the expression is being used in the math examples, where it is contrasted with stretched out solution. Perhaps it is an allusion to lassoing or lassoing in.)
"The people we are looking for," explained the EDS futurist Jeff
Wacker, "are people who can not only catch a problem, but quickly come
up with a solution that will fix the problem for good, so it will
never happen again...They see the problem, stop the problem, and then
redesign the system so that that particular problem never, ever
happens again—and it can't be a cowboy solution." Thomas
Friedman; The World is Flat (2007)
Note that if a > 0, we get a straight-stretched out solution, with y
= 0; whereas if a < 0, we get a cowboy solution, with ... S. Jalnapurkar; Modeling and Stabilization for Mechanical Systems
(1999)
The solution on the left is called the stretched out solution, whereas
the one on the right is the cowboy solution. Lawrence Sirovich;
Trends and Perspective in Applied Mathematics (2012)
[See the two illustrations on the next page.]
The cowboy solution of solving problems through violence also
links Holly to Harry's own more rationalized state and corporate
violence, seconded by the fascist BaronKurtz, a fan who carries a copy
of Martin's The Oklahoma Kid. D. Broe; Class, Crime and
International Film Noir
Moreover, what IT specialists inside the organization deemed
“cowboy IT" reigned: rogue IT specialists implanted in locations
outside OMES headquarters would regularly jury-rig a solution to a
problem... C. Fussell and C. Goodyear; One Mission (2017)
(Snippet view)
I asked the metal benders to make me up a small scoop that we could
install under the screen, and force more air in to the system. We did,
and it worked like a champ. We had it painted to match the ship and I
anticipated that the CO would be quite pleased. He viewed it as
"cowboy engineering", and I had another black mark. A. Wagner and
U Wagner; Aloft (2005)
It is interesting to note that in the same way that we might dismiss
this as 'cowboy engineering', the control and data acquisition
systems with which many of us are comfortable, are equally readily
dismissed as 'North Seaed' by some of these smaller Gulf opererators.
Subsea Control and Data Acquisition '98 (1998)