The meaning of TBD is “to be determined” or “to be decided”.
It is the slightly more elegant and official brother of the abbreviation “idk”.
“Tbd” can be originated back into the 90’s, when most abbreviations were dreamt up on chatrooms message boards and emails.
The introduction of texting on phones helped embedding the expression into common use, during the 2000’s.
It first showed up on Urban Dictionary in a 2004 definition.
Today, it can be encountered in various contexts on the internet, although it is an expression mostly found within emails from university teachers, colleagues or bosses at our workplace.