Green’s Dictionary of Slang

1. a fool, a dullard.

1696		D’Urfey Comical Hist. of Don Quixote Pt 3 V i: No, hear me, Don Bullet-head; thou Jack-a-lent [...] thou Baboon on Cock-Horse.
1707		N. Ward Wooden World 18: Then ten to one but their Bullet-heads compound for the Lapses of ther Tongues.
1722		Defoe Hist. of Colonel Jack (1723) 167: He would have Whipp’d poor Bullet-head, (so they call’d the Negro that was to be Punish’d) to Death.
1793		T. Holcroft Lavater’s Physiognomy 102: Savages, by being distorted, acquired the appellation of bowl- or bullet-head [OED].
1848		J.R. Lowell Biglow Papers (1880) 113: He aint / No more ’n a tough old bullethead.
1865		G.A. Sala A Trip to Barbary 141: But he was no stupid savage like that sea-sick bullet-head of a lay brother.
1880		Bossier Banner (Bellevue, LA) 29 Jan. 4/2: Just as the bullet-head was saying.

2. someone with a full, part-shaved or crew-cut hairstyle; a head with such a hairstyle.

1916		Friends of France 158: When the uniform is gray, men say ‘Boche’ and [...] one sees the closely cropped bullet head of the German.
1937		I. Cameron Murder in the Legion 126: We met with a crash, blindly. My knee smashed into his face, and I felt the sickening impact of his bullet-head against my stomach.
1953		J. Michener Bridges at Toko-Ri 45: The veins stood out on Cag’s bullet head.
1959		I. & P. Opie Lore and Lang. of Schoolchildren (1977) 75: Someone with a crew-cut is a ‘Bean head’, ‘Bullet head’, or ‘Convict number 99’.
1969		P. Boyle All Looks Yellow to the Jaundiced Eye 53: Close-cropped bullet head, wattles of flesh creasing the collar of his jacket [...] a rozzer if ever there was one.
1988		A. Hollinghurst Swimming-Pool Library (1998) 172: Skinheads [...] Cretinously simplified to booted feet, bum and bullet head.