Definition of First class misdemeanant
Under the English prisons act (28 & 29 Viet., c. 126, § 67) prisoners in the county, city, and borough prisons convicted of misdemeanors, and not sentenced to hard labor, were divided into two classes, one of which was called the "first division;” and it was in the discretion of the court to order that such a prisoner be treated as a misdemeanant of the first division, usually called "first-class misdemeanant,” and as such not to be deemed a criminal prisoner, i.e., a prisoner convicted of a crime.
That's the definition of First class misdemeanant in Black's Law Dictionary 6th Edition. Courtesy of Cekhukum.com.