Poppadum (or pappadam, pappadum, poppadam, ad. inf.) is a flatbread from India, made with lentil flour. It can be unseasoned, or seasoned with pepper or garlic. When deep-fried, it puffs up grandly; it can also be grilled.
If you’ve run out of lentil flour, you can purchase poppadums in Indian and some other Asian markets.