an "individual or pressure group that sets out to influence government action."
"a committee organized to raise funds to elect or defeat candidates for political office in order to promote certain policies or legislation, often in support of special interests."
a group of "people who try to influence government to support the industry or particular concerns that they belong to or support."
"lobby." The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide, edited by Helicon, 2018. Credo Reference, https://sc4.idm.oclc.org/login?qurl=https://search.credoreference.com/content/entry/heliconhe/lobby/0?institutionId=5065.
"political action committee (PAC)." Chambers Dictionary of World History, edited by Bruce Lenman, and Hilary Marsden, Chambers Harrap, 3rd edition, 2005. Credo Reference, https://sc4.idm.oclc.org/login?qurl=https://search.credoreference.com/content/entry/chambdictwh/political_action_committee_pac/0?institutionId=5065.
"special interest group." Dictionary of Politics and Government, edited by P. H. Collin, A&C Black, 3rd edition, 2004. Credo Reference, https://sc4.idm.oclc.org/login?qurl=https://search.credoreference.com/content/entry/acbgovtpol/special_interest_group/0?institutionId=5065.
Below are just a few examples of interest groups, PAC's, and lobbies. OpenSecret.org's 527s: Advocacy Group Spending can help you locate more.