#if 0
...stuff
#endif
Or block comment (if there are no other comments)
/*
...stuff
*/
But there is no such thing in bash, so the common hack is
: '
...stuff
'
i.e., use the : (no-op) operator and then the entire block to be
commented goes into a single-quoted string!
But even more simpler is:
if false; then
... stuff
fi
why not!? :=)