When some errant drops of windshield washer fluid from the car in front of you land on your own windshield, thus allowing an ineffective yet "free" cleaning.
Jim: "I really need to refill my windshield cleaner. I have bird shit caked on here from last week."
Mike: "Just keep tailing that SUV and you might stumble into some serendripity."
The fortunate discovery of Marijuana while looking for something unrelated. The resulting find will likely be very old and dry, but is nonetheless gladly received.
Last night I was looking for change in the sofa cushions and found some serendipity weed. Shit was real dry but still did the trick.
The action of making happy discoveries, by accidents and sagacity, of some thing not initially in quest of.
'I lost a needle in a hay stack last week, however whilst looking for it I found the farmers daughter' - I had to consider this (as she was pretty and willing) a stroke of serendipity.