packaged cooked rice
Refers to pre-cooked rice sold in sealed packs, often shelf-stable or frozen, common in convenience stores and supermarkets.
I bought a pack of cooked rice at the convenience store and heated it in the microwave.
レトルトご飯 specifically refers to retort-pouch cooked rice, while 包装米飯 is a broader term for any packaged cooked rice.
無菌包装米飯 is aseptically packaged cooked rice, a subset of 包装米飯 with a longer shelf life.
Compound of 包装 (packaging) + 米飯 (cooked rice).