The most-signigicant bit of an 8-bit character, which is on in character values 128--255. Also called the high bit, "alt bit" (alternate bit) or hobbit. Some terminals and consoles (see space-cadet keyboard) have a META shift key. Others (including, *mirabile dictu*, keyboards on IBM PC-class machines) have an ALT key. See also bucky bits.
Historical note: although, in modern usage shaped by a universe of 8-bit bytes, the meta bit is invariably hex 80 (octal 0200), things were different on earlier machines with 36-bit words and 9-bit bytes. The MIT and Stanford keyboards (see space-cadet keyboard) generated hex 100 (octal 400) from their meta keys.