Literal translation
The time it takes to kill a donkey with blows of figs, or of fists
Meaning
an extremely long time, an eternity
Explanation
Names an extremely long stretch of time, an eternity, used to say of someone slow that before they finish, there's time to kill a donkey by pelting it with figs. The image deliberately plays on the absurd : figs are soft and would have no effect, which makes the implied length of time all the more dizzying. The variant with punches is less amusing but just as unrealistic, since the donkey wouldn't stand for it.