Names of meals are used without articles.

When did you have dinner?

Is dinner ready?

Mother is cooking dinner.

While they were at breakfast, the letters were brought in. (Austen)

I have finished breakfast, ring the bell. (Ch. Bronte)

The definite article is used when the nouns are modified by a particularizing attribute or when the situation makes them definite.

The dinner we had to-day was very substantial.

The dinner was a success.

The indefinite article is used if the name of a meal is modified by a descriptive attribute.

After a hearty breakfast the four gentlemen sallied forth to walk to Gravesend. (Dickens)