This is the 5172nd most frequent Dutch word.
jelle
"Jelle" is a Dutch given name, typically male, and does not have a standalone definition apart from being used as a personal name.
Here, 'Jelle' is a proper noun, specifically a person's name.
Jelle is een geweldige vriend.
Jelle is a wonderful friend.
In this sentence, 'jelle' could hypothetically be used as a noun representing some piece of clothing (note: 'jelle' as a common noun doesn't exist in standard Dutch).
Waarom draag je een jelle, is het zo koud buiten?
Why are you wearing a jelle, is it so cold outside?
Again, 'Jelle' is utilized as a proper noun referring to a person.