This refers to when two or more people encounter each other in completely coincidental fashion. You might notice your old classmate from three countries away is now your waiter in a place you had no reason to expect them in, and you might say “wow, what a small world”. You might notice two people who you know from completely different spheres miraculously know each other. You might recognize by chance that your penpal has made a cameo at a venue you’re at.
But what was your most profoundly coincidental encounter?
One of my (otherwise random) WoW guild members had my grandma as his kindergarten teacher.
One of my former WoW guild members and I worked for the same company and had coordinated a job for me out of state (couple day install) a week before I met them at our first guild meet. Huge multinational and we had never interacted prior nor worked in a situation that we would.