See example at Seventh-Day.
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British Dictionary definitions for seventh-day adventist
Protestant theol a member of that branch of the Adventists which constituted itself as a separate body after the expected Second Coming of Christ failed to be realized in 1844. They are strongly Protestant, believe that Christ's coming is imminent, and observe Saturday instead of Sunday as their Sabbath
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012