frontline
//ˈfrʌntˌlaɪn//
Noun
1
The foremost position in a military conflict; the area where opposing forces engage in combat.
The soldiers were sent to the frontline to defend their country.
2
The leading or most important position in an activity, field, or movement.
She is at the frontline of medical research.
Adjective
frontlineCanonical form
1
Relating to or situated at the forefront of an activity, especially in direct contact with customers, patients, or the public.
Frontline staff deal with customer complaints every day.