This is the 2442nd most frequent Polish word.
biegu
The Polish word "biegu" means "of the run" or "of the course" (genitive singular form of "bieg").
The word 'biegu' is used in the context of a physical activity, specifically running, and is in the genitive case which indicates the 'during' aspect.
Podczas biegu poczułem się bardzo zmęczony.
During the run, I felt very tired.
Here, 'biegu' is metaphorically used to mean 'course' or 'progress', again in the genitive case referring to the project's progression.
W trakcie biegu projektu pojawiły się różne trudności.
During the course of the project, various difficulties arose.
In this sentence, 'biegu' refers to the motion or progress of the car, indicating a physical (not human-based) action.