Wiktionary
n. (context computing English) A security scheme for file level security (as opposed to traditional user, group levels, or the somewhat stricter role levels.) Abbreviated ACL.
Wikipedia
An access control list (ACL), with respect to a computer file system, is a list of permissions attached to an object. An ACL specifies which users or system processes are granted access to objects, as well as what operations are allowed on given objects. Each entry in a typical ACL specifies a subject and an operation. For instance, if a file object has an ACL that contains (Alice: read,write; Bob: read), this would give Alice permission to read and write the file and Bob to only read it.
Usage examples of "access control list".
Suddenly his monitor lit up with an access control list warning message.
As subjects access objects such as files and directories, NT checks the subject's token with the Access Control List (ACL) of the object and determines whether to allow the access or not.