The definition of aka [or a/k/a] in U.S. law, as defined by lexicographer Arthur Leff in his legal dictionary, is: abbreviation of “also known as” when someone uses other initials, a nickname, the name of a girl, or a married woman`s name. This is a preliminary summary of an upcoming entry in the Encyclopedia of Law. Please check later to get full admission. legal abbreviation of “also known as”. See Aliases. Abbreviation of “also known as” when someone uses other initials, a nickname, the name of a girl or husband. Example: Harold G. Snodgrass, aka Harry Snodgrass, aka H. G. Snodgrass, aka “Snuffy the Snod.”