The phrase "final rinse" refers to the last step of cleaning or washing something, where it is thoroughly rinsed to remove any remaining soap or dirt. Full definition
Add into water, not directly on laundry, during final rinse cycle. (seventhgeneration.com)
Usually with the marketed diaper soaps I have to do more rinses and add soap to the first rinse to have diapers that smell decent but with the homemade, no soap in the rinse, no extra final rinses and not even a hint of stink! (theecofriendlyfamily.com)
Rinse the brush under warm running water for a quick final rinse. (mindbodygreen.com)