The board may, by rule adopted under section 742.10 of the Revised Code, establish definitions of “terminal pay” and “salary” that differ from those in divisions (K) and (L) of section 742.01 of the Revised Code. In establishing the definitions, the board may use elements of the compensation provisions of the United States Internal Revenue Code and the Internal Revenue Code form W-2, as those provisions are interpreted by the internal revenue service of the United States department of treasury.