Organized Team Activities in the National Football League off-season.

Orthodontic Technicians Association, the professional body representing orthodontic technicians in the United Kingdom.

Office of Technology Assessment, a United States Congress agency disbanded in 1995.

Ochratoxin A, a mycotoxin.

Operational transconductance amplifier in electronics.

Over-the-air television or Terrestrial television, the traditional method of television broadcast signal delivery.

Over The Air Bitmap, a mechanism for sending images via SMS.

Over-the-air programming, a method of providing mobile devices with new software.

OpenTravel Alliance and the OpenTravel XML data format for the travel industry.

Oxford Text Archive at the University of Oxford.

OpenTravel Alliance and the OpenTravel XML data format for the travel industry.

Oxford Text Archive at the University of Oxford.