Definition of "barm"

barm¹

/bɑːm/

noun
plural barms
1. (obsolete outside dialects) bosom, lap.

barm²

/bɑːm/

noun
countable and uncountable, plural barms
1. Foam rising upon beer or other malt liquors when fermenting, used as leaven in brewing and making bread; yeast.
  Quotations
  [A]nd sometimes make the drink to bear no barm.
  c. 1595–1596 (date written), William Shakespeare, “A Midsommer Nights Dreame”, in Mr. William Shakespeares Comedies, Histories, & Tragedies: Published According to the True Originall Copies (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act II, scene i], line 25
  In 1577 yeast, called barm, is bought at 9d. the pail.
  1882, James Edwin Thorold Rogers, A History of Agriculture and Prices in England, volume 4, page 620
  And he chaffed the women as he served them their ha'porths of barm.Penguin 2006, p. 65
  1913, D[avid] H[erbert] Lawrence, Sons and Lovers, London: Duckworth & Co. […]
2. A small, round, flat individual loaf or roll of bread.

barm³

/bɑːm/

verb
third-person singular simple present barms, present participle barming, simple past and past participle barmed
1. To spurge; foam