Of food, a meal, or a person's diet: frugal, simple; meagre, sparse.

Of diet, fare, meals, etc.: Consisting of a comparatively small amount of food, esp. of a plain kind; not abundant or plentiful.

Of diet: †(a) In early use, plain, not delicate; (b) in later use, uncleanly or repulsive in quality. gross feeder, one who feeds grossly; said trans…

spec. of diet.