Cudgel vs Undefined - What's the difference?

As a noun cudgel

is a short heavy club with a rounded head used as a weapon.

is to strike with a cudgel.

lacking a definition or value.

(en noun)

A short heavy club with a rounded head used as a weapon.

The guard hefted his cudgel menacingly and looked at the inmates. The threat to swing glinted in his eye.

* 1883 , (Howard Pyle), (The Merry Adventures of Robin Hood)

Then they had bouts of wrestling and of cudgel play, so that every day they gained in skill and strength.

* Bunyan

He getteth him a grievous crabtree cudgel and falls to rating of them as if they were dogs.

* club * singlestick

To strike with a cudgel.

The officer was violently cudgeled down in the midst of the rioters, with his own beatstick no less.

* Shakespeare

I would cudgel him like a dog if he would say so.

To exercise (one's wits or brains).

(wikipedia undefined) (-)

Lacking a definition or value.

(mathematics, computing) That does not have a meaning and is thus not assigned an interpretation.

The result of division by zero is undefined .

* defined