Ayambil is a Jain austerity practice in which a person eats only one simple, tasteless meal in a day, and that meal is prepared without spices, oil, ghee, sugar, milk products, fruits, vegetables, or other rich ingredients.

It is done to practice:

• tapas: self-discipline and penance
• ahimsa: minimum harm to living beings
• vairagya: detachment from taste and attachment
• shuddhi: purification of body and mind

In many Jain traditions, Ayambil food is usually made from grains, lentils, or simple dry items, without any items that increase taste or indulgence. It is often observed during Paryushan, Ayambil Oli, or other vows.

In simple words, Ayambil means a vow of very plain eating for spiritual purification.