that is

Related to that is: that is to say

that is

In other words; or, to clarify or explain more clearly. No, I have never met him—not formally, that is. I'll be there this afternoon. That is, after about four o'clock or so. Yep, we planned to drive together. That is, if you still want to go.
See also: that
Farlex Dictionary of Idioms.

that is

Also, that is to say. To explain more clearly, in other words, as in It's on the first floor, that is, at street level, or We're coming next month, that is to say, in November. [Early 1600s] Also see under that's.
See also: that
The American Heritage® Dictionary of Idioms by Christine Ammer.

that is (to say)


1 in other words: I’m between jobs at the moment; that’s to say unemployed. It cost him a week’s wages, that is, €300.
2 used to give more information or to correct what has already been said: She’s a housewife — when she’s not teaching English, that is. Let him explain it — if he can, that is. Nobody wants to do it. Nobody except me, that is.
See also: that
Farlex Partner Idioms Dictionary

that is

To explain more clearly; in other words: on the first floor, that is, the floor at street level.
See also: that
American Heritage® Dictionary of the English Language, Fifth Edition.
See also:
  • that is to say
  • explain (oneself)
  • explain oneself
  • explain yourself
  • (all) dressed up
  • dressed up
  • dress up
  • NTTAWWT
  • IANA
  • IANAE
References in classic literature
He 'ave assured the angry American woman that I go at once.
The Man Upstairs and Other Stories
I have sent for you to ask that my pocket-book, dressing-case, and clothes be at once restored to me, and that I be provided with the means of continuing my journey without a moment's further delay."
The Vanished Messenger
If you think that by killing men you can prevent some one from censuring your evil lives, you are mistaken; that is not a way of escape which is either possible or honourable; the easiest and the noblest way is not to be disabling others, but to be improving yourselves.
Apology
It is more and more plain to me that I am being made the subject of an experiment, in which Sir James and the physician are equally interested.
The Two Destinies
No one is to know anything about it until I have grown so strong that I can walk and run like any other boy.
Secret Garden
"Certainly not," answered the Linnet, "that is the beginning."
The Happy Prince and Other Tales
Yet I believe that I am right in assuming that for the moment London is the headquarters of your friends, and that Lucille is here?"
The Yellow Crayon
"Would you then shut the books and exchange places with this thing that is only an appetite and a desire, a marionette of the belly and the loins?"
John Barleycorn
I was lying when I said just now that I was a spiteful official.
Notes from the Underground
Everything is ruined--my reputation, my self-respect, all that I have in the world!
Poor Folk
You would have been less amiable in my eyes had there NOT been this little unwillingness; but allow me to assure you, that I have your respected mother's permission for this address.
Pride and Prejudice
Are the young ladies and all the family quite well?' seems so pointed, that I blush.
David Copperfield
It was the first time that I had heard her speak so of De Griers: consequently, I was momentarily awed into silence by this expression of resentment.
Gambler
You must know, senor, that I am called the bachelor Samson Carrasco.
Don Quixote
"Shall you think I am horribly greedy," she asked, "if I say that I should like something to eat?
The Kingdom of the Blind