The online Macquarie dictionary says:
adjective haughtily disdainful or contemptuous, as persons, their expression, bearing, etc. [Latin superciliōsus]Dictionary.com says:
adjectiveWordorigins.com has the history and I was interested to see it comes originally from a facial expression:
haughtily disdainful or contemptuous, as a person or a facial expression.
superciliousHowever, it seems to me it can be used also in a wider sense, to relate to the tone in a piece of writing, because I came across this quote at The Acheh times:
Date of Origin 16th c.
The etymological notion underlying supercilious is of raising the ‘eyebrows’ as a sign of haughty disdain. It comes from Latin superciliōsus, a derivative of supercilium ‘eyebrow’, hence ‘haughtiness’. This was a compound noun formed from the prefix super- ‘above’ and cilium ‘eyelid’ (source of the English biological term cilium ‘hair-like process’ (18th c.), whose meaning evolved via an intermediate ‘eyelash’).
Geoffrey Norman, regarding your article about college football and the significance of football relative to the disastrous events of the past week, I appreciated it on the whole, but found it to be slightly supercilious in tone when talking about those who might have caused the atrocities. We should be angry with them and we should demand that payment be made for the evil done, but believing we are better than they are will not only not help in achieving those goals, but it will also prove to be incorrect. —— Jan Perkins in 'Readers' Reactions to Terrorist Attacks'; ESPNThere are plenty of examples on the internet of people speaking in a 'supercilious tone', so it seems to me that since writing is a way of expressing speech, therefore it can be used for spoken or written attitudes. Here's one example, from The Man With The Broken Ear by Edmond About:
"No, sir," replied Fougas in a most supercilious tone, "I'm in want of nothing, and I'd rather die than accept anything from an Englishman! If I'm calling the conductor, it's only because I want to get into a different car, and cleanse my eyes from the sight of an enemy of the Emperor."