the central and all-important part: His work was the be-all and end-all of his existence.
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British Dictionary definitions for be-all and end-all
the ultimate aim or justification: to provide help for others is the be-all and end-all of this group
often jocular a person or thing considered to be beyond improvement
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