Question

A alpha particle is a

Answer 1

An alpha particle ... one of the things that come shooting out of
some radioactive decay events ... is a package of two protons
and two neutrons.

Looking at it another way, it's a Helium nucleus ... an atom of
Helium without any electrons.

Answer 2

A alpha particle is a "particle that contains two protons and two neutrons that are together produced in the process of alpha decay."

Hope this helps!