An irritable or habitually unpleasant person.
A dirty, senile, or otherwise unpleasant patient.
An opponent in combat or in training.
An undesirable hospital patient, or a patient who does not need medical care.
A patient who does not respond to medical treatment.
A stupid, awkward, or oafish person.
An inept trainee or serviceperson.
A conical chamber at the breech of the bore in heavy ordnance, especially in mortars.