In his comment, Mohammed notes that the word appears in a paper, available here: http://www.michaeltye.us/Access.html ,Tye, Michael and Brian McLaughlin (1998), "Is Content-Externalism Compatible with Privileged Access?" in "The Philosophical Review." This is a dense paper of academic philosophy studded with technical terms such as "externalism." From context: "We see, then, that principle (RA), the introspective evidence thesis, the alternative thoughts thesis, and privileged access form an incompatible quadrad. It follows that no one can consistently hold all four theses. e see, then, that principle (RA), the introspective evidence thesis, the alternative thoughts thesis, and privileged access form an incompatible quadrad. It follows that no one can consistently hold all four theses." It seems clear from context ("no one can consistently hold all four theses" in an "incompatible quadrad") that it means a set of four of SOMETHING, and that quadrad must be one of three things: a) just a synonym for "tetrad" (and a bad one), or b) a word with a technical meaning in philosophy for a group of four SOMETHINGS, or c) the authors' own neologism. It isn't coming up when I try some Internet dictionaries of philosophy. I don't like it as a word because it is mixing a Latin-derived root ("quad-") with a Greek-derived ending ("-ad"). I don't have any kind of classical education, but a classically-educated gentleman of the Victorian era would find this mixing of Greek and Latin disturbing. The "proper" sequence is monad, dyad, triad, tetrad, pentad; hexad; heptad; octad, ennead; and decade.

Peachey, WHERE did you find it? _I_ don't think there's such a word as "quadrad." I think it's a misspelling of "quadrat." Either that or a mistaken guess at a the name for set of four, which is a either a "tetrad" if you want Greek-derived words, or a "quartet" if you want Latin-derived words. Or a neologism. "The word you've entered isn't in the dictionary. Click on a spelling suggestion below or try again using the search bar above." m-w.com. Not in my electronic Webster's Third. Not in dictionary.com. Not in thefreedictionary.com. No Wikipedia article about it.

It's a synonym of the word "square" which is a mathematical shape.

Interesting.... it's a fairly obscure word, but we can understand it because we see a Latin root. You did look it up as well, didn't you?

Please give us the context. What's the sentence, as best you can remember it, in which you saw the word, and what was the topic?