Simple past tense and past participle of fortress.(verb)
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Use "fortressed" in a sentence
"The heavily-buttressed idea about the invincibility of Wall Street -- the fortressed embodiment of Big Corporate Control of our land, our sea, our air, our country and even our DNA -- just got Occupied."
"It is in this connection that the two capital cities of Srinagar and Jammu have become as good as fortressed with additional deployment of police and paramilitary forces."
"But more seriously it goes on to say that any drop off in violence in Baghdad is because the sectarian cleansing is complete in most areas and there are fortressed enclaves of Sunnis surrounded by Shiites."