Source : Webster's Revised Unabridged Dictionary (1913)

Regimentals \Reg`i*men"tals\ (-talz), n. pl. (Mil.)
   The uniform worn by the officers and soldiers of a regiment;
   military dress; -- formerly used in the singular in the same
   sense. --Colman.

Source : WordNet®

regimentals
     n : the military uniform and insignia of a regiment