unexpectedly

Adverb

• without advance planning
  • they met accidentally
    

• in a way that was not expected
  • her brother showed up at the wedding out of the blue
    

Related words

• Synonyms: 
  by chance , accidentally , circumstantially , out of the blue
• Antonyms: 
  intentionally , deliberately , designedly , on purpose , purposely , advisedly , by choice , by design