1. adjective Relating to or containing nuanced details and minutiae that require such specific knowledge or insight as to be unintelligible or irrelevant to outsiders. Usually hyphenated. The novel is so overwrought with long, inside-baseball descriptions of the publishing world that the plot, as may be appreciated by the common reader, is largely lost in the process.

2. noun An approach containing or concerned with nuanced details and minutiae requiring such specific knowledge or insight as to be unintelligible or irrelevant to outsiders. I hate going to dinner with my wife's economist friends. There's always so much inside baseball between them that I'm always left with nothing to talk about.