What is Peremptory?

Legal Definition
Absolute; positive. A final determination to act without hope of renewing or altering. Joined to a substantive, this word is frequently used in law; as peremptory action; F. N. B. 35, 38, 104, 108; peremptory nonsuit; Id. 5, 11; peremptory exception; Bract. lib. 4, c. 20; peremptory undertaking; 3 Chit. Pract. 112, 793; peremptory challenge of jurors, which is the right to challenge without assigning any cause. Inst. 4, 13, 9 Code, 7, 50, 2; Id. 8, 36, 8; Dig. 5, 1, 70 et 73.
-- Bouviers Law Dictionary
Legal Definition
Imperative; absolute; not admitting of question, delay or reconsideration. Positive; final; decisive; not admitting of any alternative. Self-determined; arbitrary; not requiring any cause to be shown.
See also
-- Black's Law Dictionary
Legal Definition
Final; positive; conclusive.
-- Ballentine's Law Dictionary