This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

n. A specialist who is primarily concerned with a subspecialty within a larger specialty.

"Out of desperation, insomniacs may problem-solve independently, most commonly resorting to alcohol as a self medication, not understanding that there is in this country, more so than anywhere else, a certified subspecialist sleep medicine community which exists to solve exactly these problems."