accidental

/ˌæksɪˈdɛntl/
adjective
  1. Happening without being planned or intended; by chance.
    • The discovery of penicillin was accidental.
    • He made an accidental error when he typed the wrong number.
    • An accidental meeting with an old friend made her day.
What does "accidental" mean? | whatsthatwordmean | whatsthatwordmean