A person who does something only occasionally.
Created for a specific occasion.
Acting in the indicated role from time to time.
Occurring or appearing irregularly from time to time, but not often.
Intended for use as the occasion requires.
Relating to, amounting to, causing, or caused by a physical or mental disorder.
Having properties which are counterintuitive or difficult to handle.
Pertaining to pathology.
Having properties that cause unusually bad behaviour, especially regarding correctness or performance.