rockhead

plural rockheads

1. geographyThe surface of the bedrock beneath soil cover.

   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.

   2012, P. B. Attewell, I. W. Farmer, Principles of Engineering Geology, page 457

2. The fish Bothragonus swanii, a variety of poacher.
3. derogatoryslangA stupid person.

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

   2016, James Young, Rise of the Dust Child

plural rockheads

1. slangA fan of rock music.

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

   1997, New York Magazine, volume 30, number 15, page 65

   1 more example

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

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