• IPA: /ˌæksəˈdɛnt(ə)li/

accidentally

1. In an accidental manner; by chance#Noun|chance, unexpectedly.

   Synonyms: casually, fortuitously, Thesaurus:accidentally

   He discovered penicillin largely accidentally.

2. Unintentionally.

   He accidentally exposed the bacteria to mold spores.

   • 1899, Knut Hamsun, “Part I”, in George Egerton [pseudonym; Mary Chavelita Dunne Bright], transl., Hunger: Translated from the Norwegian, London: Leonard Smithers and Co. […], OCLC 560168646 ↗; republished New York, N.Y.: Alfred A. Knopf, October 1920 (December 1920 printing), OCLC 189563 ↗, page 14 ↗:

     As I arrived at the foot of the hill I overtook two ladies, whom I passed. As I did so, I brushed one of them accidentally on the arm.

• intentionally, deliberately, designedly, on purpose, purposely, advisedly, by choice, by design

• accident

• French: accidentellement
• German: versehentlich
• Italian: casualmente, accidentalmente
• Portuguese: acidentalmente
• Russian: случа́йно
• Spanish: accidentalmente