Chance upon Definition 1 of 1Pro Tip 1/3Unexpected Discovery Used when someone discovers something they weren't looking for. I chanced upon an old friend in the market. Pro Tip 2/3Positive Surprises Often implies a pleasant or beneficial find. We chanced upon a quaint little cafe. Pro Tip 3/3Casual Tone The phrase has a casual, conversational feel, not very formal. They chanced upon a deal while shopping.