Source : Webster's Revised Unabridged Dictionary (1913)

Thrum \Thrum\, v. t. [imp. & p. p. {Thrummed}; p. pr. & vb. n.
   {Thrumming}.]
   1. To furnish with thrums; to insert tufts in; to fringe.

            Are we born to thrum caps or pick straw? --Quarles.

   2. (Naut.) To insert short pieces of rope-yarn or spun yarn
      in; as, to thrum a piece of canvas, or a mat, thus making
      a rough or tufted surface. --Totten.

Thrum \Thrum\, v. i. [CF. Icel. ?ruma to rattle, to thunder, and
   E. drum.]
   1. To play rudely or monotonously on a stringed instrument
      with the fingers; to strum.

   2. Hence, to make a monotonous drumming noise; as, to thrum
      on a table.

Thrum \Thrum\, n. [OE. thrum, throm; akin to OD. drom, D. dreum,
   G. trumm, lump, end, fragment, OHG. drum end, Icel. ?r["o]mr
   edge, brim, and L. terminus a limit, term. Cf. {Term}.]
   [Written also {thrumb}.]
   1. One of the ends of weaver's threads; hence, any soft,
      short threads or tufts resembling these.

   2. Any coarse yarn; an unraveled strand of rope.

   3. (Bot.) A threadlike part of a flower; a stamen.

   4. (Mining) A shove out of place; a small displacement or
      fault along a seam.

   5. (Naut.) A mat made of canvas and tufts of yarn.

   {Thrum cap}, a knitted cap. --Halliwell.

   {Thrum hat}, a hat made of coarse woolen cloth. --Minsheu.

Thrum \Thrum\, v. t.
   1. To play, as a stringed instrument, in a rude or monotonous
      manner.

   2. Hence, to drum on; to strike in a monotonous manner; to
      thrum the table.

Source : WordNet®

thrum
     n : a thrumming sound; "he could hear the thrum of a banjo"
     v 1: sound with a monotonous hum [syn: {hum}]
     2: sound the strings of (a string instrument); "strum a guitar"
        [syn: {strum}]
     3: make a rhythmic sound; "Rain drummed against the
        windshield"; "The drums beat all night" [syn: {drum}, {beat}]
     [also: {thrumming}, {thrummed}]