(slang, vulgar, derogatory) Absolutely nothing.

The desire for money is the root cause of all evil.

(mathematics, complex analysis) The theorem that if a complex number is a root for a polynomial with real coefficients, the complex conjugate of that number will also be a root.

One who, or that which, roots; one that tears up by the roots. / One who roots or rummages through something.

(US, slang) One who roots for, or applauds, something.

(computer security) A set of software tools used by a third party to gain unauthorized access to a computer system and control the system while concealing itself from the user.

(transitive) To infect (a computer system) with a rootkit.

plural of rootkit

Of a plant or another thing, having no roots. / Being a wanderer; having no ties to a particular locale. / (computing) Without (the use of) a root user account.

(of an animal) to dig into the ground, with the snout. / (of a person) to search for something from a drawer, closet, etc.; to dig out.