What is the meaning of Alle?

Alle, or Allez, is a form of encouragement in climbing. It means "go" or "come one" in French.

When people shout "allez" at others, it's the same as shouting "come on", "you can do it", it's just a form of encouragement that is very common in climbing.

Different countries and languages may have their own word of encouragement besides allez, but I think that alle is by far the most common.