cattle dung: cow droppings, dried and burned as everyday cooking fuel
This word turns up once in the whole Bible, in Ezekiel 4:15, and it names one thing: the droppings of cattle. Ezekiel has been told to act out the coming siege of Jerusalem by baking his rationed bread over a fire of human waste (גֵּל). As a priest he is appalled, since nothing unclean has ever passed his lips, and God answers by granting him cow dung to burn instead.
Dried dung was ordinary fuel in a land with little firewood, as it still is in much of the world. Patted into flat cakes and dried in the sun, it burns low and steady, which is what a clay oven needs. So the concession is less strange than it sounds today: God is not handing the prophet something exotic but the commonest cooking fire there was. The horror in the sign lay in the human waste, and in what a fire scraped together like that says about a city under siege, where fuel and food alike run out.
Later Jewish writing kept using this word for exactly the same thing, dried cattle dung, and even for rough vessels made of it, which is strong confirmation that the sense is right. Ezekiel's text spells the word with one set of letters while the traditional way of reading it aloud supplies another, but both are the same word, and the old Greek and Latin translations render it plainly as cow dung. What scholars argue over is the word's family: the same letters also spell a Hebrew word for a viper (צִפְעוֹנִי) and a much-debated word in Isaiah usually taken as "offshoots" (צְפִיעָה). Older lexicons tied all of them to one idea of something pushed or squeezed out, while modern ones keep them apart as words that merely look alike.