What is the meaning of drone?

noun

• Stingless male bee in a colony of social bees (especially honeybees) whose sole function is to mate with the queen.
• An unchanging intonation.
  • synonyms: monotone, droning
• Someone who takes more time than necessary; someone who lags behind.
  • synonyms: dawdler, laggard, lagger, trailer, poke
• An aircraft without a pilot that is operated by remote control.
  • synonyms: pilotless aircraft, radio-controlled aircraft
• A pipe of the bagpipe that is tuned to produce a single continuous tone.
  • synonyms: drone pipe, bourdon

verb

• Make a monotonous low dull sound.
  • usage: "The harmonium was droning on"
• Talk in a monotonous voice.
  • synonyms: drone on