Definition:Lowest Common Multiple/Integers/Definition 1

Definition
For all $a, b \in \Z: a b \ne 0$, there exists a smallest $m \in \Z: m > 0$ such that $a \divides m$ and $b \divides m$.

This $m$ is called the lowest common multiple of $a$ and $b$, and denoted $\lcm \set {a, b}$.

Also see

 * Equivalence of Definitions of Lowest Common Multiple