We can give you a better answer if you give us some more information, particularly the context. What were you reading when you came across the term?I I've read on this link (( http://henningkarlsen.com/electronics/p_utft_analog_clock.php )) the code of the Project: UTFT Analog Clock and was at the beginning of the code written :
/ / Enable (1) or disable (0) VT100 terminal mode
/ / Enable this if your terminal program supports VT100 control sequences.
/ / The Serial Monitor in the Arduino IDE does not support VT100 control sequences.
/ / If using the Serial Monitor the line ending should be set to 'No line ending'.
# define VT100_MODE 1