rockhead

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From rock +‎ head.

rockhead (plural rockheads)

1. (geology) The surface of the bedrock beneath soil cover.
   • 2012, P. B. Attewell, I. W. Farmer, Principles of Engineering Geology, page 457:

     This type of area, with reasonably well-defined rockheads under glacial and lacustrine deposits, probably represents optimum conditions for the adoption of seismic exploration techniques.

2. The fish Bothragonus swanii, a variety of poacher.
3. (slang, derogatory) A stupid person.
   • 2016, James Young, Rise of the Dust Child:

     Men seemed just as superfluous as women, a bunch of rockheads running around punching each other and getting hot and sweaty about guns.

From rock +‎ -head.

rockhead (plural rockheads)

1. (slang) A fan of rock music.
   • 1997, New York Magazine, volume 30, number 15, page 65:

     […] an apparent betrayal of electronica's more oblique, less suburban ethos in favor of a record the rockheads like.

   • 2015, Edward A. Hagan, To Vietnam in Vain: Memoir of an Irish-American Intelligence Advisor, 1969-1970, page 46:

     The rarest species was a Protestant although I'd bet that the majority of Ivy League rockheads in the 1950s were Prots.

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