The Collaborative International Dictionary of English v.0.48:

Overhead \O`ver*head"\, adv.
   Aloft; above; in or attached to the ceiling or roof; in the
   story or upon the floor above; in the zenith.
   [1913 Webster]

         While overhead the moon
         Sits arbitress.                          --Milton.
   [1913 Webster]

   Note: Also used adjectively; as, an overhead crane, gear,
         etc.
         [1913 Webster]

   Overhead engine, a vertical steam engine in which the
      cylinder stands above the crank.

   Overhead work, a general term in manufactories for
      countershafting and gearing, when overhead.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

overhead \o"ver*head`\, n.
   1. same as overhead expenses.
      [PJC]

   2. A compartment on a train, bus, or airplane used for
      storage of luggage or accessory equipment; called also
      overhead compartment.
      [PJC]

   3. (Sports) A stroke with a racket in which the ball is
      struck with the racket over the head, moving in a downward
      motion; also called overhead stroke.
      [PJC] Overhead charges

WordNet (r) 3.0 (2006):

overhead
    adv 1: above your head; in the sky; "planes were flying
           overhead"
    2: above the head; over the head; "bring the legs together
       overhead"
    adj 1: located or originating from above; "an overhead crossing"
           [ant: subsurface, surface]
    n 1: the expense of maintaining property (e.g., paying property
         taxes and utilities and insurance); it does not include
         depreciation or the cost of financing or income taxes [syn:
         operating expense, operating cost, overhead, budget
         items]
    2: (computer science) the processing time required by a device
       prior to the execution of a command [syn: command processing
       overhead time, command processing overhead, command
       overhead, overhead]
    3: (computer science) the disk space required for information
       that is not data but is used for location and timing [syn:
       disk overhead, overhead]
    4: a transparency for use with an overhead projector [syn:
       viewgraph, overhead]
    5: (nautical) the top surface of an enclosed space on a ship
    6: a hard return hitting the tennis ball above your head [syn:
       overhead, smash]

Moby Thesaurus II by Grady Ward, 1.0:

76 Moby Thesaurus words for "overhead":
   above, abovestairs, airward, aloft, aloof, budget, budget items,
   burden of expenditure, carrying charge, ceiling, charges, cost,
   cost of living, cost-of-living allowance, cost-of-living index,
   costs, direct costs, disbursals, distributed costs, eaves,
   elevated, expenditures, expense, expense account, expenses,
   general expenses, high, high up, housetop, in the air,
   in the clouds, indirect costs, labor costs, lantern, liabilities,
   maintenance, material costs, on high, on stilts, on the peak,
   on tiptoe, operating costs, operating expense, outlay, over,
   overhead, penthouse, plafond, prime cost, raised, replacement cost,
   ridgepole, roof, roof garden, roof-deck, roofage, roofing,
   roofpole, rooftop, rooftree, shingles, skylight, skyward, slates,
   straight up, swindle sheet, tiles, tiptoe, to the zenith, top,
   unit cost, up, upper, upstairs, upward, upwards



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

overhead

   1. Resources (in computing usually processing time or storage
   space) consumed for purposes which are incidental to, but
   necessary to, the main one.  Overheads are usually
   quantifiable "costs" of some kind.

   Examples: The overheads in running a business include the cost
   of heating the building.  Keeping a program running all the
   time eliminates the overhead of loading and initialising it
   for each transaction.  Turning a subroutine into inline
   code eliminates the call and return time overhead for each
   execution but introduces space overheads.

   2.  information, such as control, routing, and
   error checking characters, that is transmitted along with the
   user data.  It also includes information such as network
   status or operational instructions, network routing
   information, and retransmissions of user data received in
   error.

   3. Overhead transparencies or "slides" (usually 8-1/2" x 11")
   that are projected to an audience via an overhead (flatbed)
   projector.

   (1997-09-01)