The Collaborative International Dictionary
Trub \Trub\, n. [Cf. Truffle.] A truffle. [Obs.]
Wiktionary
n. 1 (context brewing uncountable English) The layer of sediment that appears at the bottom of the fermenter after yeast has completed the bulk of the fermentation. 2 (context obsolete English) A truffle.
Wikipedia
Trub is one of the largest municipalities of Switzerland (62 km²) in size, but not in population. It is located in the Emmental region of the canton of Bern in the administrative district of Emmental.
In the process of brewing beer, trub is the term used for the lees, or layer of sediment, left at the bottom of the fermenter after the yeast has completed the bulk of the fermentation. It is composed mainly of heavy fats, proteins, and inactive yeast.
Trub also refers to the material, along with hop debris, left in the boil kettle or hopback after the wort has been transferred and cooled. Brewers generally prefer that the bulk of the trub be left in the kettle rather than stay in contact with the fermenting wort. Although it contains yeast nutrients, its presence can impart off-flavors in the finished beer.
The term has its origins in the German word trübe (also trüb), which means cloudy, via the brewing and winemaking terms Trubstoff (cloudy + material) and Weintrub (wine + cloudy).
Usage examples of "trub".
Pullings, and he explained to the others that long ago, when first made lieutenant, he had seen that the Doctor loved trubs, so he had gone out into the forest, the New Forest, where he lived by land, and had dug him a basket, by way of welcome aboard: and Mowett had composed a song.
The talk grew more cheerful: pigs at home, how best dressed - pigs, wild, on a remote island in the South China Sea, that had nourished Captain Aubrey and his people for a great while - a little tame black sow at Pullings' father's farm on the edge of the New Forest that would find you a basket of trubs, or truffles as some called them, in a morning, winking and grinning at you with each trub, never eating a single one herself.