Flaxseed, also known as linseed, is a leading source of plant-derived omega-3 fatty acids and dietary fiber. Grinding the glossy brown seeds into fine particles is what unlocks their nutritional benefits, as whole flaxseeds are so small they usually pass through the intestinal tract undigested.
The term "meal" is generally used to describe any grain, legume, nut or seed that's been ground into a powdery substance. Just as cornmeal is ground corn, flaxseed meal is simply ground flaxseed. A product labeled "whole ground flaxseed meal" could just as accurately be called "ground flaxseed" or "flaxseed meal."
The high fat content responsible for much of a flaxseed's health benefits is also what gives it a relatively short shelf life. Stored properly, whole flaxseed typically keeps up to a year. Ground flaxseed doesn't last nearly as long, however, because more of its oils are exposed to air. Flaxseed is rancid when it smells like oil paint.
When buying prepackaged flaxseed meal, check its expiration date and odor to ensure freshness. Any ground flaxseed you don't plan to use right away should be placed in an air-tight container and kept in the freezer, where it usually lasts for about six months.