What is Registration?

Legal Definition
Recording; Inserting ip an official register; the act of making a list, catalogue, schedule or register, particularly of art official character or of making entries therein. In re Supervisors of Election (C. Ct) 1 Fed. 1. See Registration of stock.
-- Black's Law Dictionary
Legal Definition
The method of proof prescribed for ascertaining the electors who are qualified voters. See 119 N. Y. 175, 23 N. E. 523.
-- Ballentine's Law Dictionary