This is the 1637th most frequent German word.
zufällig
Accidental; random; by chance.
Here, 'zufällig' is used as an adverb to indicate that the meeting was by chance or coincidence.
Ich habe meinen alten Freund zufällig im Park getroffen.
I happened to meet my old friend in the park.
In this sentence, 'zufällig' is used to politely inquire if someone knows the time, suggesting an incidental nature implicitly.
Weißt du zufällig, wie spät es ist?
Do you happen to know what time it is?
Here, 'zufällige' is used as an adjective to describe the noun 'Ereignis' as random or occurring by chance.