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Webster 1913 Edition

Noun.

One who mutters.

Noun.

A grumbler; one that mutters.

mutterer ‎(plural mutterers)

One who mutters.
- 1926, Rafael Sabatini, Bellarion the Fortunate, Chapter 3,
  "To accuse a priest!" said someone in a tone of indignation, and a murmur arose at once in sympathy. ¶ It moved the young officer to mirth. He half-swung on his heel so as to confront those mutterers.
- c. 1954, Jack Kerouac, Untitled poem, in Book of Sketches, 1952-57, Penguin, 2006, p. 239,
  I, mutterer to / myself in childhood French […]