Wikipedia
Buschwhacker is a term for NASCAR drivers who are regulars in the top-level Sprint Cup Series but who also compete on a regular basis in the second-tier Xfinity Series. The original coinage of the term Buschwacker refers to Anheuser-Busch's longtime title sponsorship of the series through their Busch Beer brand. A new term, Claim jumper, was coined to refer to Nationwide Insurance's sponsorship of the series from 2008 to 2014. In 2015, the term Signal Pirate was created in reference to current sponsorship of the series by Comcast's Xfinity brand.
The practice is controversial due to Cup drivers such as Kyle Busch, Mark Martin and Kevin Harvick (numbers one, two, and three all time in wins in the Xfinity Series) entering a large portion of races over the course of the season and dominating the races in superior equipment, taking good finishes, competitive rides and sponsorship, and exposure away from both development drivers and veterans who are regulars in the series. Many NASCAR experts, however, contend that without Cup drivers and the large amount of fan interest and sponsorship they attract, the series would cease to exist.
Due to NASCAR rules changes that took effect in 2011, drivers must now select one of the top three touring series to be eligible the driver' championship. This prevents Cup Series regulars from also competing for points in the lower series. Before these changes, the last series regular to win the Nationwide Series points title was Martin Truex Jr., winning in 2004 and 2005. Despite these changes, Cup drivers have continued their dominance, shifting their focus to winning the owner's championship. In the five years following the rule change, the owners champions were the #60 team of Roush Fenway Racing with Carl Edwards racing the majority of the season in 2011, the #18 with various Joe Gibbs Racing drivers in 2012, and the #22 of Team Penske from 2013 to 2015 with Brad Keselowski and Joey Logano running the majority of the races.