What does GAPD stand for?

Garrett Auxiliary Power Division - Military contractor

Geiger-mode avalanche photo diode detector (SAUS)

Glyceraldehyde-3-Phosphate Dehydrogenase (STED)

Glyceraldehyde Phosphate Dehydrogenase - Organic chemistry (MAH)

Government and Aeronautical Products Division - Honeywell, Inc.