Real Dictionary

white out in American English
to cover (errors in copy) with a white correction fluid

white out in British English
to lose or lack daylight visibility owing to snow or fog
noun: an atmospheric condition consisting of loss of visibility and sense of distance and direction due to a uniform whiteness of a heavy cloud cover and snow-covered ground, which reflects almost all the light it receives

white-out in American English
a quick-drying fluid, typically white, applied with a small brush to a piece of paper so as to cover typed or written errors and make a blank surface for corrections
to cover with this fluid

White-Out in British English
noun: a proprietary brand of white correcting fluid