29 CFR 4208.2 - Definitions.
In addition, for purposes of this part:
Eligible employer means the employer, as defined in section 4001(b) of ERISA, as it existed on the date of its initial partial or complete withdrawal, as applicable. An eligible employer shall continue to be an eligible employer notwithstanding the occurrence of any of the following events:
(1) A restoration involving a mere change in identity, form or place of organization, however effected;
(4) An acquisition by or of, or a merger or combination with another trade or business.
Partial withdrawal year means the third year of the 3-year testing period in the case of a partial withdrawal caused by a 70-percent contribution decline, or the year of the partial cessation in the case of a partial withdrawal caused by a partial cessation of the employer's contribution obligation.