1 : an act of going completely around a track or over a course when you are running, swimming, etc.
The race is 12 laps long.
With one lap remaining, the race was still close.
the last/final lap of the race
(US) He was swimming/doing laps in the pool. [=he was swimming from one end of the pool to the other and then back again]
◊ The winner of a race often takes a victory lap (US) or lap of honour (British) by going around the track or over the course alone one more time as a way to celebrate.
2 : a part of a journey
They were in the last lap [=stage, leg] of their trip home from Europe.