IPA: /ˌɪn.sɪˈdɛn.t̬ə.li/
KK: /ˌɪn.sɪˈdɛn.t̬əl.i/
In a way that is not the main focus or is added as a side note.
Incidentally, I heard that the meeting has been postponed.
Incidentally → It is formed from "incidens" (from Latin, meaning falling upon or happening) and the suffix "-ly" (meaning in a manner of). The word "incidentally" refers to something that happens by chance or as a secondary occurrence.
Think of something that 'falls upon' you unexpectedly — that's what incidentally means, as it refers to something happening by chance.