It’s a good question. Others may have other definitions, but for our purposes a COMMONER is someone that either is, or is an advocate for, the common man (note I am being old school here, using the inclusive masculine). A commoner is someone that is conscious of, and works for the progress of, the common good; someone that seeks the best for the most, starting at the bottom. There is no formulaic prescription for solutions implied in the term. A commoner is not a communist, nor a corporatist.
Some other relevant definitions:
Christian Democracy – a political ideology and movement that began in large measure as a response to the anti-Christian and anti-cultural nature of the French Revolution and Marxism on the one hand, and the anti-worker and anti-social nature of Social Darwinism and laissez-faire capitalism on the other. It is distinct from Christianity as a religion, and most Christian democratic parties today do not have a religious criterion for membership or service. Christian democracy as an ideology is a form of communitarianism. It is a political philosophy focusing on the health of the community in all areas of community existence. This community orientation is often considered right-leaning in regard to moral and cultural issues and left-leaning in regard to social justice, labor and socio-economic issues. Christian democratic parties generally claim a strong social conscience, in the sense of great respect for the dignity of the human person from conception to natural death, emphasizing the alleviation of poverty, and maintenance of a basic level of societal protection keeping the weak from abandonment and destitution, and the regulation of market forces for the common good (advocating a “social market economy”). It may also be seen as liberal as it upholds human rights and individual initiative (read personal responsibility). It may be seen as federalistic and traditional in that it emphasizes sphere sovereignty and subsidiarity, and maintaining local and regional cultural distinctives, as well as upholding universal traditions. It may be seen as green in that it advocates positive stewardship of the creation, especially through using renewable energy, and avoiding activities that destroy the environment. Christian democracy is a significant force in the political mainstream of Europe and Latin America, but is less common on other continents. Christian democratic parties in Latin America are generally more inclined to be on the center-left regarding economics, while their European counterparts tend to be closer to the political center, or center-right, on economic issues.
Christian Democrat – someone that advocates Christian Democracy, or is a member of a Christian democratic party; in the American context the term is sometimes used in reference to Christian members of the Democratic Party, though this is a misuse of the term (largely due to ignorance of the term in the American political scene) — note that in the American context a Christian Democrat is equally likely to be a member of either the Democratic or Republican parties, or no party at all (given the de facto binary choice offered by the system)
Pilgrim Progressive – a term I use (coined by me?) to refer to someone that could have been a follower of William Jennings Bryan at the turn of the 20th century; someone that is progressive but not liberal (according to the original meaning of that term); someone that is a commoner (as previously defined here) motivated by Christian or other religious belief; for example if someone were a Jew or Muslim progressive that advocated universal health care, a living wage (and other economic freedom measures), and was pro-life on abortion, that person might consider himself a “pilgrim progressive”; the term intentionally plays off the title of John Bunyan’s wonderful classic Pilgrim’s Progress, and intentionally makes reference to the first American settlers that sought religious freedom and societal progress from a Puritan perspective
Catholic Social Teaching – a body of teachings that have grown in tandum with Christian Democracy; they are official teaching of the Catholic Church, but they are amenable to and embraceable by Christians of all stripes (I say this as a non-Roman Catholic — and a Calvinistic Baptist), and non-Christians as well; a set of social teachings that begin with the principles of human dignity, solidarity, and subsidiarity; the teachings were first understood as such from the encyclical letter of Pope Leo XIII called Rerum Novarum