Following on work done by NGOs (non-governmental organizations) such as Oxfam [1], I use this term in my classes to refer to the practice by ruling elites (comprising the bourgeoisie and its political allies) in capitalist democracies of rigging the political system to its advantage for the specific purpose of accumulating as much wealth as possible outside of the normal capitalist economic machinery--such as creating/investing in legitimate businesses.
In other words, it is a form of corruption that is not readily evident to the public that involves a range of mechanisms: from semi-kleptocratic practices to regulatory capture of government agencies; from unmerited tax-breaks to outright tax-avoidance by hiding wealth off-shore; from undermining the rule of law by stacking the highest courts (e.g. the U.S. Supreme Court) in their favor to pumping out biased-research through think-tanks they establish and fund; from legislative capture at all levels of government (by means of revolving-door high-paid lobbyists, astronomical campaign donations, gerrymandering, etc.) to stoking the bottomless appetite of the military industrial complex; from scapegoating racial/ethnic minorities to manipulation of the content of the mass media given its majority ownership of it; and so on.
Folks, it is important to emphasize this point: capitalism requires inequality (consider: if everyone was a member of the upper class, who would do all the real work, such as building roads, teaching kids like you in schools, picking tomatoes, collecting garbage, cleaning hotel rooms, washing dishes in restaurants, looking after patients in hospitals, assembling cars in auto plants, and so on, and so on). So, what exactly is the problem with the nature of inequality today in most countries around the world? It is that it is inequality that has not come about through capitalism but through the unfair use of political power by the upper class, examples of which are listed above. Now, here is the key question for ya: we live in a democracy (here in the U.S.), so how is the upper class able to get away with this?
Note: this term (political capture) cannot apply to societies that are non-democratic because in such societies political capture is already baked-in--it goes with the territory, so to speak.
NOTES
1. See, for example: Political Rigging: A Primer on Political Capture and Influence in the 21st Century, by Janine R. Wedel, Nazia Hussain, and Dana Archer Dolan, Oxfam America, 2017, available here: https://www.oxfamamerica.org/explore/research-publications/political-rigging/