tba stands for 'to be announced'. You see it on posters, schedules, invitations, and websites where one piece of information is not ready yet — usually the time, the place, the price, or the speaker. So a concert poster might say 'Support act: TBA', or a meeting schedule might have 'Venue: TBA'. It is written English, not spoken; if you were talking, you would just say 'we haven't decided yet' or 'they'll tell us later'. You will see it written TBA, tba, or T.B.A. — all the same. Read it honestly, though: sometimes TBA really does mean the decision is coming soon, and sometimes it is a polite way of saying nobody has sorted it out and might not for a long while. Two close relatives are worth knowing: TBC ('to be confirmed'), where there is a plan but it is not final, and TBD ('to be decided' or 'to be determined'), where the choice has not been made at all.