Search Result for "attosecond": 
Wordnet 3.0

NOUN (1)

1. one quintillionth (10^-18) of a second; one thousandth of a femtosecond; 



WordNet (r) 3.0 (2006):

attosecond
    n 1: one quintillionth (10^-18) of a second; one thousandth of a
         femtosecond