If something is tacan, it means it is not correct or exact.
Tacan things are not good. People don't like them.
Examples:
The answer was tacan.
She gave a tacan description of the event.
His guess was tacan.
The map was so tacan, it led us to the wrong place!
Her cooking is always tacan; she never follows the recipe.
The clock was tacan, and we missed the start of the movie.