The Collaborative International Dictionary of English v.0.48:

Overdrive \O`ver*drive"\, v. t. & i.
   To drive too hard, or far, or beyond strength.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

overdrive \o"ver*drive`\, n.
   1. (Machinery) A gearing device which causes the drive shaft
      of an automobile or other machine to rotate at a speed
      greater than that of the engine crankshaft.
      [PJC]

   2. (Automotive) The gear setting of a motor vehicle at which
      the overdrive[1] is operative; as, cruising at 80 mph in
      overdrive.
      [PJC]

   3. Hence: [fig.] A state of unusually intense activity; as,
      when they got their new supercomputer, their research
      kicked into overdrive; one look at her made his heart jump
      into overdrive; -- used mostly of the activities of
      persons or groups.
      [PJC]

WordNet (r) 3.0 (2006):

overdrive
    n 1: the state of high or excessive activity or productivity or
         concentration; "Troops are ready to go into overdrive as
         soon as the signal is given"; "Melissa's brain was in
         overdrive"
    2: a high gear used at high speeds to maintain the driving speed
       with less output power
    v 1: drive or work too hard; "The teacher is overworking his
         students"; "Overdriving people often suffer stress"
    2: make use of too often or too extensively [syn: overuse,
       overdrive]

Moby Thesaurus II by Grady Ward, 1.0:

63 Moby Thesaurus words for "overdrive":
   Hydromatic, automatic transmission, burden, busy, carry too far,
   cogwheel, differential, differential gear, drive, exaggerate,
   exhaust, fag, freewheel, gear, gear train, gearbox, gearing,
   gearshift, gearwheel, go overboard, go to extremes, go too far,
   high, intermediate, keep busy, know no bounds, low, neutral,
   oppress, overact, overcarry, overdevelop, overdo, overelaborate,
   overemphasize, overexercise, overexert, overexpend, overindulge,
   overlabor, overplay, overreact, overspend, overstrain, overstress,
   overstudy, overtask, overtax, overtrain, overuse, overwork,
   pass all bounds, protest too much, rack, reverse,
   standard transmission, stick shift, sweat, synchromesh, task, tax,
   transmission, work



The Free On-line Dictionary of Computing (30 December 2018):

Overdrive

    An Intel Pentium processor which fits into a
   socket designed to accomodate an Intel 486, or into a
   special upgrade socket on the motherboard.

   (1995-03-27)