What is the omnibus motion rule?

Rule 15, Sec. 8. Omnibus motion. Subject to the provisions of section 1 of Rule 9, a MOTION attacking a pleading, order, judgment, or proceeding shall include all objections then available, and all objections not so included shall be deemed WAIVED.

Under the omnibus motion rule, all available grounds for objection in attacking a pleading, order, judgment, or proceeding should be invoked all at the same time; otherwise, they are deemed waived. An exception to this is the court's power to dismiss the case motu proprio based on Rule 9, Section 1. (Please see possible changes in the Rules brought about by the 2020 amendments.)