IPA: /ˌsɛr.ənˈdɪp.ɪ.təs/
KK: /sɛrənˈdɪpɪtəs/
Describing something that happens by chance in a happy or beneficial way.
Their meeting was serendipitous, leading to a wonderful partnership.
Serendipitous is derived from 'serendipity' (coined by Horace Walpole in 1754, based on the Persian fairy tale 'The Three Princes of Serendip', where the princes made discoveries by accidents and sagacity) and the suffix '-ous' (meaning full of). The word 'serendipitous' describes events that occur by chance in a happy or beneficial way.
Think of the story of the 'Three Princes of Serendip' who made happy discoveries by accident — that's why serendipitous means finding something good unexpectedly.