If it had only 1 term it would be a MONOMIAL.
If it had only 2 terms it would be a BINOMIAL.
If it had only 3 terms it would be a TRINOMIAL.
But yours has 4 terms. So all you can do is say it is a POLYNOMIAL.
For some reason they never coined a word "quadranomial" or "tetranomial", :)
For all I know, in other languages there may be a word
specifically for 4-term polynomials, but not in English. So we
just call it a polynomial. FYI, its degree is 7.
Edwin