Is there a "standard" name for $n \times n$-matrices whose square is $-1$ times the identity matrix?

97 Views Asked by At

I have seen the name “skew involution” in a problem in at least one book but none of my colleagues who work in abstract algebra, geometry or linear algebra have ever heard of this name, although they agree it is a reasonable name. I have used the term “imaginary unit” for such matrices and my colleagues agree that is also a reasonable name, but I wonder if there is a standard name in the literature.