True or False: if $X$ and $Y$ are indicator variables for $A$ and $B$, then $X+Y$ is an indicator variable for $A \cup B$

True or False: if $X$ and $Y$ are indicator variables for $A$ and $B$,
then $X+Y$ is an indicator variable for $A \cup B$

Suppose $X$ and $Y$ are indicator variables for events $A$, $B$
respectively, then $X+Y$ is always an indicator variable for $A \cup B$.
Also I need some help with the definition of an indicator variable.