young gun

: being in the first or an early stage of life, growth, or development

: junior

: of an early, tender, or desirable age for use as food or drink

: young persons : youth

: immature offspring

: a single recently born or hatched animal

: a piece of ordnance usually with high muzzle velocity and comparatively flat trajectory

: a portable firearm (such as a rifle or handgun)

: a device that throws a projectile

: to fire on

: shoot

: to open up the throttle of so as to increase speed