The ordinal form of the number zillion.(adjective)
The person or thing in the zillionth position.(noun)
One of a zillion equal parts of a whole.(noun)
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Use "zillionth" in a sentence
"At the Javits Center this week, I caught a fresh-faced salesman giving his zillionth demonstration of a new shopping technology."
"It's baby steps, but maybe I am slowly coming to understand that a small contribution, a modest gift or a kind word matter more now than the zillionth eloquent diatribe about the villains."
"I should be writing a book right now and not responding to the zillionth linkless attack on the ills of the blogosphere, this time from NPR's outgoing ombuds, Alicia Shepard, who blames the "dark side" and "lousy job" of the blogosphere for NPR's own admittedly unclear (not to mention wrong-headed, in my view) memo forbidding staff from so much as stepping near the Jon Stewart Restoring Sanity rally."