Use 'indigestible' when explaining why certain foods cause stomachaches or digestion problems. I avoided the heavy meal; it seemed indigestible.
Pro Tip 2/3
Negative Connotation
'Indigestible' often implies that the food is not just heavy, but unpleasant and should be avoided. The greasy meal was indigestible and unappealing.
Pro Tip 3/3
Metaphorical Usage
Sometimes 'indigestible' describes situations or experiences that are hard to accept or process, not just food. The news of the sudden tragedy was indigestible.