A colloquial expression meaning that something is a matter of indifference or unimportant to someone. It is a synonym of 'egal' (doesn't matter) or 'wurst' (doesn't matter).
example
Ob wir heute oder morgen ins Kino gehen, ist mir eigentlich völlig toast.
Whether we go to the movies today or tomorrow really doesn't matter to me at all.
Usage tips
Only with "sein"
The word 'toast' (doesn't matter) is used as an adjective only predicatively, meaning it always appears together with a form of the verb 'sein' (to be). You cannot put it before a noun.
EXAMPLE
Deine Meinung ist mir in dieser Sache völlig toast.
Your opinion on this matter doesn't matter to me at all.
Dative construction
The person to whom something is a matter of indifference is always in the dative. The structure is: Etwas ist [Person im Dativ] toast.
EXAMPLE
Ob wir den Bus verpassen, ist ihm anscheinend toast.
Whether we miss the bus apparently doesn't matter to him.
Register: colloquial
This expression is very colloquial and is mainly used in spoken language among friends or in informal situations. You should avoid it in formal contexts.
EXAMPLE
Mir ist toast, was die anderen über mein Hobby denken.
I don't care what the others think about my hobby.
Compare with
antonym
Toast vs wichtig
important
'wichtig' and 'toast' are opposites when 'toast' is used colloquially to mean 'egal' or 'unwichtig' (doesn't matter / unimportant). 'wichtig' says that something has significance and should be paid attention to. 'toast' says that something does not matter to someone. This use of 'toast' is very casual and is not equally common everywhere. In neutral situations, it is better to say 'egal' or 'unwichtig'.
Toast
Welche Serie wir heute schauen, ist mir eigentlich toast.
I honestly don't care which series we watch today.
wichtig
Am Telefon erklärt mein Kollege, welche Unterlagen für das Treffen wichtig sind.
On the phone, my colleague explains which documents are important for the meeting.