Abbreviation for "Top Qualifier". The top qualifier is one who achieves the most laps in the shortest amount of time.

For example:

Racer E - 27 laps - 5:10.23 (TQ)
Racer B - 27 laps - 5:11.98

Both Racer E and Racer B returned 27 laps. But how long it took them to accomplish this is equally important. If Racer B would have finished at least 1.76 seconds before Racer E, Racer B would have won.