Magnetic anomaly detector , a scientific instrument and anti-submarine warfare detection device
M.A.D., a fictional evil organization led by Dr. Claw from the cartoon series InspectorGadget
Mandibular advancement device , an appliance worn in the mouth to treat obstructive sleep apnea or snoring
Market Abuse Directive , European company law on insider dealing and market manipulation
Mean absolute difference , a measure of statistical dispersion
Median absolute deviation , a statistical measure of variability, more resistant to outliers than other measures
Meg and Dia , American indie rock band
MAD (programming language) , for Michigan Algorithm Decoder, a computer programming language
MIFARE Application Directory, a data structure on MIFARE contactless chips
Militärischer Abschirmdienst , the Military Counterintelligence division of the German Army
MPEG Audio Decoder , an audio decompression software
Multi-conjugate Adaptive optics Demonstrator , astronomical method of using multiple guide stars and deformable mirrors to sense and correct for the distortions produced by turbulence in Earth's atmosphere
Multi-wavelength anomalous dispersion , a technique used in X-ray crystallography
Museum of Arts & Design , located in New York City
Mutual assured destruction , a doctrine of military strategy
Mastertronic's Added Dimension (or "Mastertronic Added Dimension"), a sub-label owned by defunct UK software publisher Mastertronic
Make A Difference , an Indian NGO
Mothers against decapentaplegic , a protein of the SMAD family
