Toast vs Undefined - What's the difference?

As a noun toast

is toast (toasted bread or salutation).

lacking a definition or value.

(-)

Toasted bread.

I ate a piece of toast for breakfast.

All toasters toast toast .

A proposed salutation (e.g. to say "cheers") while drinking alcohol.

At the reception, there were many toasts from the well-wishers.

A person, group, or notable object to which a salutation with alcohol is made; a person or group held in similar esteem.

He was the toast of high society.

(slang) Something that will be no more; something subject to impending destruction, harm or injury.

If I ever get my hands on the guy that stole my wallet, he’s toast !

(slang, Jamaica) Extemporaneous narrative poem or rap.

(computing) A transient, pop-up informational window

* french toast * propose a toast * Texas toast * toaster * toast of the town

(en verb)

To lightly cook by browning via direct exposure to a fire or other heat source.

We liked to toast marshmallows around the campfire.

To grill, lightly cook by browning specifically under a grill or in a toaster

Top with cheese and toast under the grill for a few minutes.

To engage in a salutation and/or accompanying raising of glasses while drinking alcohol in honor of someone or something.

We toasted the happy couple many times over the course of the evening.

To warm thoroughly.

I toasted my feet by the fire.

(slang, Jamaica) To perform extemporaneous narrative poem or rap.

(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