1.verbTo access the value or object located in a memory location stored in a pointer or another value interpreted as such; to access a value being referenced by something else.
"Attempting to dereference a null pointer often results in a crash."
2.verb(in operating systems derived from Unix) To operate on the file or directory pointed to by a symbolic link, rather than on the link itself.
"With the find command, any symbolic links appearing after -follow will be dereferenced."