What is the meaning of overdrive?

noun

• The state of high or excessive activity or productivity or concentration.
  • usage: "Troops are ready to go into overdrive as soon as the signal is given"; "Melissa's brain was in overdrive"
• A high gear used at high speeds to maintain the driving speed with less output power.

verb

• Drive or work too hard.
  • usage: "The teacher is overworking his students"; "Overdriving people often suffer stress"
• Make use of too often or too extensively.
  • synonyms: overuse