Wiktionary
n. (context idiomatic English) Someone who dresses and acts as a cowboy but has none of the skills.
Wikipedia
Drugstore Cowboy is a 1989 American crime drama film directed by Gus Van Sant, written by Van Sant and Daniel Yost, and is based on an autobiographical novel by James Fogle. The film stars Matt Dillon in the title role, Kelly Lynch, Heather Graham and William S. Burroughs. It marked Van Sant's second film as director.
At the time the film was made, the source novel by Fogle was unpublished. It was later published in 1990, by which time Fogle had been released from prison. Fogle, like the characters in his story, was a long-time drug user and dealer.
Usage examples of "drugstore cowboy".
Suddenly, back at the small town where it all began, outside the lighted window of Geety's drugstore, overlooking the square, the phantom lover, the ghostly drugstore cowboy, is glimpsed again.