The definition of plagiarism varies by context. Technically, you avoid the charge of plagiarism by citing sources, but that ignores the issue of what you are using the quoted material to do.
A quotation should be used to support your argument, not to express your argument. In other words, if you are arguing a point and you want to say, John Smith agrees with me, then you quote a few lines from John Smith that say the same thing you have already said (in different words).
Or if you are making a point that differs from that of John Smith, you quote a few lines from John Smith to show that you are representing his views correctly, and they you go on to explain why John Smith is wrong.
Or you are making an argument that depends on certain key facts being true, which some people may doubt, so you quote the renowned John Smith to prove that the facts on which your argument depends are true.
In each of these cases, your argument exists in full in your own words, independent of the quotations. The quotations are there to support what you are claiming about the works of other that you are citing, or to support a fact that you are asserting. In each case, if you removed the quotes, the reader would still understand your argument in full. They might be less inclined to accept it, without the evidence you have quoted, but they would be able to fully understand it.
Contrast this to when you use the work of others to make some of all of your case. For instance, suppose you write an article Why we should return to the gold standard and in it you write, "As John Smith argues in his article Gold is Good and then go on to reproduce a big chunk of the article. This is not technical plagiarism in the sense that you failed to acknowledge your source. But it is moral plagiarism in that you are using John Smith's words to make the argument, not merely to support it. You did not do any work other than reading John Smith's work and copying and pasting.
In addition to being moral plagiarism, this is also a copyright violation, since this usage does not fall within the scope of fair use. (Citing sources make absolutely no difference in copyright law.)
If you were to paraphrase most of John Smith's work and only quote snippets, this would (probably) avoid the copyright charge, but it would still be moral plagiarism because you are still not doing the work yourself, just paraphrasing the work of another.
You can, of course, paraphrase the arguments of other in support of your own argument. But you need to have an argument of your own that constitutes the raison d'etre of your article, or morally, at least, you are still plagiarizing.