This is the 575th most frequent Hebrew word.
במרץ
With vigor or energetically.
In this case, "במרץ" conveys an energetic and impassioned style or approach to an activity.
כשהוא מנגן בגיטרה, הוא עושה זאת במרץ ובתשוקה.
When he plays the guitar, he does so energetically and with passion.
In this sentence, "במרץ" is used as a time indicator referencing the month of March.
הפרחים פורחים במרץ כשהאביב מתחיל.
The flowers bloom in March when spring begins.
Here, "במרץ" means energetically or with passion, describing the manner of progress.