Sentence:  ...a better machine is a <WSD>petaflop</WSD> machine. A <WSD>petaflop</WSD> is a quadrillion flops, a quadrillion floating-point operations per second, so a <WSD>petaflop</WSD> machine is a thousand times as fast as a teraflop machine, or a million times as fast as a Cray Y-MP8. The <WSD>petaflop</WSD> machine will exist by the year 2000, or soon afterward. 
Meaning of the word marked with <WSD> tags:  a quadrillion (10¹⁵) (floating point operations) per second.