In media coverage of recent events in Egypt, one word is used more cautiously than any other: revolution.
While that doesn't hold true for editorials, the fact is that major news outlets have avoided using the term in their reporting. You would be hard-pressed to find an instance of the word in non-opinion pieces (outside of quotations) in the online incarnations of New York Times, CNN, the Wall Street Journal, MSNBC, or Fox News. The Daily Beast is comfortable using the word in headlines and tags, but not in the body of any article.
It appears that the Associated Press has embargoed "revolution." Words like uprising, revolt, upheaval, chaos, and unrest are much easier to come by; "anti-government protests" appears to be the safest phrase. A search for "Egypt revolution" on Al-Jazeera English returns a single occurrence of the word: the last paragraph of an opinion piece.
That's with good reason—after all, we're not sure if what's happening in Egypt is really a revolution, at least not yet. Merriam-Webster provides three definitions for the word:
a : a sudden, radical, or complete change
b : a fundamental change in political organization; especially: the overthrow or renunciation of one government or ruler and the substitution of another by the governed
c : activity or movement designed to effect fundamental changes in the socioeconomic situation
This is certainly a sudden, radical, and complete change in the visible character of Egypt, and there's definitely "activity or movement designed to effect fundamental changes." But Hosni Mubarak is still the president and the ruling government remains intact. One could argue that a revolution is only a revolution once it's over. For example, the marches in Tiananmen Square? Protests. Bahrain in 1990? Intifada. Student demonstrations in Burma in 1988? Uprising. All ended in quashed dissent at the hands of the military and a more-or-less complete return to the status quo. Revolution was arrested.
For a succinct explanation of the distinction between a revolution and something else, look no further than CNN's Fareed Zakaria.