any of various very large marine turtles; esp a flesh-eating turtle of the W Atlantic: Caretta caretta
an iron tool consisting of a long handle ending in a ball or bulb used to melt tar or to heat liquids
archaic a fool or dunce
‘Where hast thou been, Hal?’ ‘With three or four loggerheads amongst three or fourscore hogsheads’ — Shakespeare
at loggerheads
in quarrelsome disagreement
For nearly two years, England played with a manager and captain at loggerheads — Today
literally ‘a head made of a logger [= block of wood]’ and hence ‘a person with a disproportionately large head’