To access the thing to which a pointer points,
i.e. to follow the pointer. E.g. in
C, the declarations
int i;
int *p = &i;
declare i as an integer and p as a pointer to integer. p is
initialised to point at i ("&i" is the address of i - the
inverse of "*"). The expression *p dereferences p to yield i
as an
lvalue, i.e. something which can appear either on the
left of an
assignment or anywhere an integer expression is
valid. Thus
*p = 17;
would set i to 17. *p++ is not the same as i++ however since
it is parsed as *(p++), i.e. increment p (which would be an
invalid thing to do if it was pointing to a single int, as in
this example) then dereference p's old value.
The
C operator "->" also dereferences its left hand argument
which is assumed to point to a
structure or
union of which
the right hand argument is a
member.
At first sight the word "dereference" might be thought to mean
"to cause to stop referring" but its meaning is well
established in jargon.