Third.
The phrase 'meter tercera' is not directly translated as 'third' in English. It's an idiomatic expression in Spanish, specifically used in the context of driving a vehicle. It metaphorically means 'to step it up' or 'to take it to the next level' by referring to shifting to the third gear in driving. Just like how shifting to a higher gear in driving accelerates the speed, 'meter tercera' implies increasing pace, intensity or making more effort in a situation. Though 'tercera' means 'third', the whole expression 'meter tercera' holds a different implicit meaning.
We need to put it in third gear to finish this project on time.
This phrase is used metaphorically to express that they need to speed up their efforts for the completion of a project.
If I want to finish the race, I need to put it in third gear.
Here, the phrase is used to convey the idea of increasing one's pace or effort in order to accomplish a goal, in this case, finishing a race.
Let's put it in third gear to get to the appointment on time.
The given phrase is used to refer to hurrying or accelerating the pace to reach an appointment on time.