Find the word definition

Wiktionary
eigenspinor

n. (context physics English) A quantum mechanics vector that represents the spin state of a particle

Wikipedia
Eigenspinor

In quantum mechanics, eigenspinors are thought of as basis vectors representing the general spin state of a particle. Strictly speaking, they are not vectors at all, but in fact spinors. For a single spin 1/2 particle, they can be defined as the eigenvectors of the Pauli matrices.