Idiom Definition:
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"out of the blue"  
    suddenly and unexpectedly     
            
Synonyms: 
abrupt, expeditious, fast, flash, fleet, hasty, headlong, hurried, immediate, impetuous, impulsive, precipitous, quick, rapid, rush, rushing, shocking, startling, stunning, sudden, surprise, surprising, unanticipated, unaware, unawares, unforeseen, unplanned, unprepared
 
    
