  In this article, all rings are commutative with nonzero identity. Let $M$ be
an $R$-module. A proper submodule $N$ of $M$ is called a classical prime
submodule, if for each $m\in M$ and elements $a,b\in R$, $abm\in N$ implies
that $am\in N$ or $bm\in N$. We introduce the concept of "classical 2-absorbing
submodules" as a generalization of "classical prime submodules." We say that a
proper submodule $N$ of $M$ is a classical 2-absorbing submodule if whenever
$a,b,c\in R$ and $m\in M$ with $abcm\in N$, then $abm\in N$ or $acm\in N$ or
$bcm\in N$.
