Translation guide
In Japanese, 'old rice' typically refers to rice from a previous harvest, not spoiled rice. The most common term is 古米 (こまい), used in contrast to 新米 (しんまい, new rice).
The speaker wants to refer to rice that is not from the current year's harvest, often with a slightly different texture or cooking requirement.
Standard term for rice harvested in a previous year. It is commonly used in grocery stores and cooking contexts.
When cooking this old rice, please use a bit more water.
Rice harvested two or more years ago. It is even older than 古米 and may have a more noticeable change in quality.
Rice that is two years old absorbs water even less readily than one-year-old rice.
Literally 'last year's rice'. A more casual, descriptive way to refer to old rice.
We still have some rice from last year left.
The speaker wants to refer to rice that was cooked earlier and has become dry, hard, or stale.
Cold, leftover cooked rice. Often used for fried rice or other dishes.
Using cold leftover rice makes fried rice turn out fluffy and separate.
Leftover rice. A general term for rice that remains after a meal.
It's convenient to freeze leftover rice.
The speaker wants to refer to rice that is no longer safe to eat due to age or improper storage.
新米 (しんまい) is newly harvested rice, prized for its moisture and flavor. 古米 (こまい) is rice from the previous year, which is drier and often requires more water when cooking. In stores, 古米 is cheaper and clearly labeled.
If you mean rice that has been intentionally aged for better flavor (like aged sake rice), that is 熟成米 (じゅくせいまい) or 古酒米 (こしゅまい), not 古米. 古米 simply means non-new-crop rice.
In summer, you need to be careful about rice going bad.