Definition: The stymie is an archaic part of golf that was included in singles match play until it was eliminated from the Rules of Golf in 1952.
When "stymies" were in effect, golf balls on the green were not marked and lifted in singles match play unless the two balls were within six inches of each other. A "stymie" occurred when another ball was directly in the putting line of your ball. Since that ball was not lifted (unless it was within 6 inches of your ball), you'd have to putt over or around it.
See the FAQ, "What were stymies, and when were they eliminated from golf?" for more on stymies.
