Wiktionary
n. (context idiomatic English) Used vegetable oil purposed for use as biodiesel.
Wikipedia
Yellow grease, also termed used cooking oil (UCO), used vegetable oil (UVO), recycled vegetable oil, or waste vegetable oil (WVO) is recovered from businesses and industry that use the oil for cooking.
It is used to feed livestock, and to manufacture soap, make-up, clothes, rubber, and detergents. Due to competition from these other industrial sectors, the EIA estimates that less than a third of yellow grease could be spared for biodiesel production annually.
It is distinct from brown grease; yellow grease is typically used frying oils from deep fryers, whereas brown grease is sourced from grease interceptors.
Usage examples of "yellow grease".
With a broad-bladed spatula they scraped the grease from the drums and collected it in the boiling pot, then meticulously spread each drum with a fresh coating of yellow grease.
So while wet gravel would roll across a steel table smeared with thick yellow grease, the dry diamond would stick fast.
Here and there, reflections of the town lights, like a rancid yellow grease, were smeared across the clouds, but the night was deep and nearly ideal for our purposes.
Dead fish and birds hung suspended, rotting and half-eaten, bones coated with a yellow grease.
Along the ridge of the Candy Deep, neat and sweet smelling in its new paint, thick with yellow grease and waiting only to be fitted together, lay the dismembered mill.
Then he pulled a leather bag from a pouch in his undershirt, squeezed from it a quantity of yellow grease, and briskly rubbed it over his exposed skin, causing the serpent to gleam as though newly-arrived from some humid southern jungle.