Much discussion goes on in health care circles as to what to call what chiropractors do.   The answer is simple.  Chiropractors perform Specific Scientific Chiropractic adjustments.   A chiropractic adjustment is a specific procedure of moving spinal vertebrae for the purpose of correction of a vertebral subluxation.  According to the Association of Chiropractic Colleges, "A subluxation is a complex of functional and/or structural and/or pathological articular changes that compromise neural integrity and may influence organ system function and general health."

Is the term manipulation the same as an adjustment? To answer this question lets first look in a Webster Dictionary for some synonyms of each.

Manipulation: Exploit, misuse, take advantage, control, deploy, maneuver, use, ply, swing, wield, grope, examine, finger, fondle, handle, maul, palpate, paw, probe, touch, govern, sway.

And for Adjustment: Factor, calculate, align, center, regulate, convert, scale, tune, dial, select, fine tune, finesse, modify, tweak, regulate, standardize, conform, equalize, level, set policy, alter, catalyze, change, refashion, calibrate, decide, determine, establish, resolve, set, compensate, make equal, redeem, remedy, correct, cure, fix, heal, make well, repair, restore, coordinate, attune, accommodate, conform, harmonize, integrate, proportion, reconcile, tune, correct, amend, fix, improve, mend, position, rectify, restore, right, straighten, service, maintain, adapt, balance, fit, inspect, overhaul, recondition, refurbish, regulate, repair, support.

In looking at the two it is easy to see why chiropractors use the term adjustment .  An adjustment is certainly not just random movement of spinal bones to hear a "pop" sound.  A properly given chiropractic adjustment is designed to correct interference to the nervous system from subluxations.

The International Chiropractors Association (ICA) has a policy on this subject that says it best; 

"The ICA holds that the chiropractic spinal adjustment is unique and singular to the chiropractic profession. The chiropractic adjustment shall be defined as a specific directional thrust that sets a vertebra into motion with the intent to improve or correct vertebral malposition or to improve its juxtaposition segmentally in relationship to its articular mates thus reducing or correcting the neuroforaminal / neural canal encroachment factors inherent in the chiropractic vertebral subluxation complex.
The adjustment is characterized by a specific thrust applied to the vertebra utilizing parts of the vertebra and contiguous structures as levers to directionally correct articular malposition. Adjustment shall be differentiated from spinal manipulation in that the adjustment can only be applied to a vertebral malposition with the express intent to improve or correct the subluxation, whereas any joint, subluxated or not, may be manipulated to mobilize the joint or to put the joint through its range of motion.
Chiropractic is a specialized field in the healing arts, and by prior rights, the spinal adjustment is distinct and singular to the chiropractic profession."