What is Actuary?

Legal Definition
An actuary is a business professional who deals with the measurement and management of risk and uncertainty (BeAnActuary 2011a). The name of the corresponding profession is actuarial science. These risks can affect both sides of the balance sheet, and require asset management, liability management, and valuation skills (BeAnActuary 2011b). Actuaries provide assessments of financial security systems, with a focus on their complexity, their mathematics, and their mechanisms (Trowbridge 1989, p. 7).

While the concept of insurance dates to antiquity (Johnston 1903, §475–§476, Loan 1992, Lewin 2007, pp. 3–4), the mathematics and finance needed to scientifically measure and mitigate risks have their origins in the 17th century studies of probability and annuities (Heywood 1985). Actuaries of the 21st century require analytical skills, business knowledge, and an understanding of human behavior and information systems to design and manage programs that control risk (BeAnActuary 2011c). The actual steps needed to become an actuary are usually country-specific; however, almost all processes share a rigorous schooling or examination structure and take many years to complete (Feldblum 2001, p. 6, Institute and Faculty of Actuaries 2014).

The profession has consistently ranked as one of the most desirable (Riley 2013). In various studies, being an actuary was ranked number one or two multiple times since 2010 (Thomas 2012, Weber 2013, CareerCast 2015).
-- Wikipedia
Legal Definition
A clerk in some corporations vested with various powers. In the ecclesiastical law he is a clerk who registers the acts and constitutions of the convocation.
-- Bouviers Law Dictionary
Legal Definition
In English ecclesiastical law. A clerk that registers the acts and constitutions of the lower house of convocation; or a registrar in a court Christian. Also an officer appointed to keep savings banks accounts; the computing officer of an insurance company; a person skilled in calculating the value of life' interests, annuities, and insurances.
-- Black's Law Dictionary
Legal Definition
The manager of a company.
-- Ballentine's Law Dictionary