Wiktionary
n. 1 A member of a class of individuals that receive inferior treatment. 2 (context programming languages English) (synonym of second-class object English)
Wikipedia
A second-class citizen is a person who is systematically discriminated against within a state or other political jurisdiction, despite their nominal status as a citizen or legal resident there. While not necessarily slaves, outlaws or criminals, second-class citizens have limited legal rights, civil rights and socioeconomic opportunities, and are often subject to mistreatment or neglect at the hands of their putative superiors. Instead of being protected by the law, the law disregards a second-class citizen, or it may actually be used to harass them (see police misconduct and racial profiling). Systems with de facto second-class citizenry are generally regarded as violating human rights. Typical impediments facing second-class citizens include, but are not limited to, disenfranchisement (a lack or loss of voting rights), limitations on civil or military service (not including conscription in every case), as well as restrictions on language, religion, education, freedom of movement and association, weapons ownership, marriage, gender identity and expression, housing and property ownership.
The category is normally unofficial, and the term itself is generally used as a pejorative and governments will typically deny the existence of a second class within the polity. As an informal category, second-class citizenship is not objectively measured; however, cases such as the American South under segregation, aborigines in Australia prior to 1967, apartheid in South Africa, women in Saudi Arabia under Saudi law, Dalits in India and Nepal, and Roman Catholics in Northern Ireland during the parliamentary era are all examples of groups that have been historically described as having second-class citizenry. In the present day, convicted felons and dropouts are believed to be considered second-class citizens.
By contrast, a resident alien or foreign national, and children in general, may have limited rights within a jurisdiction (such as not being able to vote, and having to register with the government), but is also given the law's protection, and is usually accepted by the local population. A naturalized citizen carries essentially the same rights and responsibilities as any other citizen (a possible exception being ineligibility for certain public offices), and is also legally protected.