Relativism: The notion that judgments depend on whoever makes them, and in particular on their (lack of) knowledge, bias, prejudice, interests, concerns etc.
That so-and-so is supposedly "relative" is almost always a rhetorical move that is intended to make rational discussion difficult or impossible, and to move matters of fact into the realm of matters of value.
The reasons that relativism is almost always a rhetorical move that is intended to make rational discussion difficult or impossible are, first, that if the truth or falsity of some judgment does depend on whomever makes it (as may be the case with some judgments of taste or preference) and not on whatever the judgment is about, there is little to disagree about or discuss, and, second, that the claim that so-and-so is relative seems to be nearly always dishonest or confused.
Note that there is no problem with the thesis that judgements do depend on - to some extent, that may vary a lot with the person or the circumstances - the (lack of) knowledge, bias, prejudice, interests, concerns etc. of whoever makes the judgment, since in fact that is trivially true.
The problem is with the further thesis that this trivially true fact would settle either that there is no truth of the matter at all (as many relativists like to argue, presumably because they have no better defense for their thesis than that it is a mere matter of taste) or that what is the truth of the matter cannot be somehow established, at some time, possibly far in the future.
In general, a useful rule of thumb about relatitivism is that - to vary Dr. Johnson - relativism is the first refuge of the scoundrel and the stupid: If you can neither defend nor argue a thesis just loudly insist that it is "relative" and "therefore" a "matter of free democratic choice". Since most people know that judgments depend also on the makers of them, and since there are many people who are none too bright, success is almost certainly guaranteed in any population of average or worse intelligence, who, not coincidentally, tend to be also precisely those who most believe that any matter whatsoever can be fairly, equitably and rationally settled by majority voting in which everyone equally participates, irrelative of intelligence, knowledge, experience, sincerity, or probity.