A "sealed bottle" refers to a bottle that has been tightly closed or covered to prevent any air or liquid from entering or escaping. It is completely closed and not easily opened unless the seal is broken. Full definition
We always kept a bottle, a sealed single serving packet of formula, and a small sealed bottle of mineral water in the diaper bag, in case of emergencies. (skepticalob.com)
Then, seal the bottle with an airtight cap to help protect your breast milk from contamination and odors while it's in the freezer. (verywellfamily.com)