The list is incomplete. Conspicuous in their absence are such fundamental behavioral terms as operant and respondent pain, for example. Dozens of pain syndromes could appear in this list as could many basic terms from laboratory pain research such as writhing response. I am open to including additional definitions if you wish to submit them.
Algology
Allodynia
Analgesia
Anesthesia
Anesthetic
Anesthesia Dolorosa
Angina
Arthralgia
Causalgia
Central Pain
Deafferentation Pain
Dermatome
Dysesthesia
Hyperesthesia
Hyperalgesia
Hyperpathia
Hypoalgesia
Hypoesthesia
Neuralgia
Neuritis
Neuopathic Pain
Neuropathy
Nociceptor
Noxious Stimulus
Pain
Pain Threshold
Pain Tolerance Level
Paresthesia
Radiculalgia
Radiculopathy
Radiculitis
Somatosensory
Suffering
Trigger Point