front line noun
plural ∼ lines [count] 1 : an area where soldiers are fighting : 1front 7a
▪ troops on the front line = front-line troops 2 : the most important and active position in a job or field of activity
▪ These researchers are on/at the front line of defense against cancer. ▪ She has been working on the front lines to educate the poor.
▪ troops on the front line = front-line troops
▪ These researchers are on/at the front line of defense against cancer. ▪ She has been working on the front lines to educate the poor.
