from The American Heritage® Dictionary of the English Language, 4th Edition
- n. One billionth (10-9) of a second.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A measure of time equal to one billionth of a second. Abbreviation: ns
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. one billionth (10^-9) of a second; one thousandth of a microsecond
The SI prefix nano- + second (Wiktionary)