49 C.F.R. § 588.4 – Definitions.

(a) Statutory definitions. All terms defined in section 102 of the National Traffic and Motor Vehicle Safety Act (15 U.S.C. 1391) are used in their statutory meaning.
(b) Motor Vehicle Safety Standard definitions. Unless otherwise indicated, all terms used in this part that are defined in the Motor Vehicle Safety Standards, part 571 of this subchapter (hereinafter “the Standards”), are used as defined in the Standards.
(c) Definitions used in this part.
Child restraint system is used as defined in S4 of 49 CFR 571.213, Child Restraint Systems.
Factory-installed built-in child restraint system is used as defined in S4 of 49 CFR 571.213.
Owners include purchasers.
Registration form means the form provided with a child restraint system in compliance with the requirements of 49 CFR 571.213, and any communication from an owner of a child restraint to the manufacturer that provides the restraint's model name or number and the owner's name and mailing address.