Steady drone

WordNet Word definitions in WordNet
n. a thrumming sound; "he could hear the thrum of a banjo" v. sound with a monotonous hum [syn: hum ] sound the strings of (a string instrument); "strum a guitar" [syn: strum ] make a rhythmic sound; "Rain drummed against the windshield"; "The drums beat ...

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Thrum \Thrum\, v. t. [imp. & p. p. Thrummed ; p. pr. & vb. n. Thrumming .] To furnish with thrums; to insert tufts in; to fringe. Are we born to thrum caps or pick straw? --Quarles. (Naut.) To insert short pieces of rope-yarn or spun yarn in; as, to thrum ...

Wiktionary Word definitions in Wiktionary
n. The sound or action of something that thrums. vb. (present participle of thrum English)