"lightening fast" is correct and is often used in informal written English.
You can use it to emphasize that something happened very quickly or was done very quickly. For example: "The cheetah ran lightening fast to catch its prey."
How do you write about skating tricks that are lightening fast, but technically complicated — and that are so visual?
Who would have thought that both Her Majesty and Prince Charles would possess the courage, let alone the lightening fast reactions, required to throw themselves in front of a sniper bullet intended for Barack Obama at a state dinner?
Browster for Firefox is a revolutionary, secure, lightening fast way to preview web pages".
It also helps that Dropbox's software is lightening fast and, well, it does just work.
As with much else in China, the change has come lightening fast.
Meantime, anyone considering the XKR 100 must also drive the more practical and still lightening fast CLK 55 AMG Mercedes; the CL55 AMG, which is also a great joy to drive (as we mention elsewhere in this article); and the marvelous new Maserati Spyder.
Pain can have the same effects on mood as depression, the big difference is that pain medication lightens mood as fast as the right anti-depressant does for someone with chronic fatigue.
One second he was slow and fluid like water, and the next he was precise and lightening-fast like a prizefighter.
It seems a leap from the commerce of shiny skyscrapers and lightening-fast bourses.
Cast in a sickly glow from the light of his computer screen, his lightening-fast fingers expose secret after secret, and soon information designed to keep America safe - information the villain swore to protect - is exposed to the entire world, including terror networks.
And, years after the lightening-fast engagement, their initial infatuation sustained them through thwarted ambitions (Lotto's, acting; Mathilde's, art), tiffs with estranged family members, and disagreements about whether they should have children.
