Wiktionary
vest-pocket
a. 1 small enough to be carry in a vest pocket or other small container. 2 By extension, anything smaller than would ordinarily be expected.
Usage examples of "vest-pocket".
A cul-de-sac with a landscaped median and old-fashioned street lights, it extended the equivalent of three blocks, ending at a vest-pocket park with an impressive monument.
While we were in New York City together, she would be staying with her maternal grandmother, a stockbroker's widow, in a queerly irrelevant enclave of dead-end streets and vest-pocket parks.