Webster's New World Medical Dictionary

q.d.
Seen on a prescription, one per day. Also
known as quotid. See also Appendix A,
“Prescription Abbreviations.”
q.h.
On a prescription, every hour. See also
Appendix A, “Prescription Abbreviations.”
q.i.d.
On a prescription, four times daily. See also
Appendix A, “Prescription Abbreviations.”
q.n.s.
On a lab report, insufficient quantity of
sample.
QRS complex
The deflections in an electrocar-
diogram (EKG) tracing that represent the ventricu-
lar activity of the heart.
q.s.
On a prescription, as needed. See also
Appendix A, “Prescription Abbreviations.”
q.3h.
On a prescription, every 3 hours. See also
Appendix A, “Prescription Abbreviations.”
QT syndrome, long
See 
long QT syndrome.
q.2h.
On a prescription, every 2 hours. See also
Appendix A, “Prescription Abbreviations.”
quack 1
A practitioner who suggests for prevention
or treatment of disease substances or devices that are
known to be ineffective.
2
Someone who pretends
to be able to diagnose or heal people but is unquali-
fied and incompetent.
quackery
Deliberate misrepresentation of the
ability of a substance, a device, or a person to pre-
vent or treat disease.
quadrant
A quarter of an area. For example, the
liver is in the right upper quadrant of the abdomen.
quadriceps 1
Any four-headed muscle.
2
The
large muscle of the thigh that comes down the bone
of the upper leg (femur) and over the kneecap
(patella), and then anchors into the top of the large
bone in the lower leg (tibia). The function of the
quadriceps is to straighten (extend) the leg. Also
known as musculus quadriceps femoris and quad.