guard baby Share definition Flag a person whos entire military carear has been in the guard. ie no active duty. "i enlisted at 18 and now i have 27 years in and im still only a MSgt b/c noboday above me has died/retired, i am a guard baby." guard baby by psedonym February 25, 2005 0 0 Get merch Get the guard baby mug. Buy Now — $32.95 See more merch