(software, object-oriented programming) A software design pattern in computer science, used with languages that provide run-time type information about objects.

(aviation, chiefly US) A ground-based radio navigation aid consisting of a pair of colocated radio beacons at the final approach fix of an ILS or IGS approach course: an NDB to guide aircraft to the approach fix, and an outer marker to alert aircraft as they pass over the station.

(American Sign Language) Any of the non-sign components of American Sign Language (facial expression, body position, head position, etc.) that provide context and tone to signs.