something to fill one's stomach; a bite to eat
Used when referring to food that is just enough to stave off hunger, often in the phrase 腹の足しになる (to serve as a snack or light meal).
One rice ball won't even fill my stomach.
It's not much, but I ate some cookies to tide me over.
Compound of 腹 (stomach) + の (possessive particle) + 足し (supplement, from 足す 'to add'). Literally 'a supplement for the stomach'.