Hypertext Webster Gateway: "bumming"
From Webster's Revised Unabridged Dictionary (1913) (web1913)
Bum \Bum\, v. i. [imp. & p. p. {Bummed}; p. pr. & vb.n.
{Bumming} (?).] [See {Boom}, v. i., to roar.]
To make murmuring or humming sound. --Jamieson.
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