The Collaborative International Dictionary of English v.0.48:

Mechanical \Me*chan"ic*al\, a. [From Mechanic, a.]
   [1913 Webster]
   1. Pertaining to, governed by, or in accordance with,
      mechanics, or the laws of motion; pertaining to the
      quantitative relations of force and matter on a
      macroscopic scale, as distinguished from mental,
      vital, chemical, electrical, electronic, atomic
      etc.; as, mechanical principles; a mechanical theory;
      especially, using only the interactions of solid parts
      against each other; as mechanical brakes, in contrast to
      hydraulic brakes.
      [1913 Webster +PJC]

   2. Of or pertaining to a machine or to machinery or tools;
      made or formed by a machine or with tools; as, mechanical
      precision; mechanical products.
      [1913 Webster]

            We have also divers mechanical arts.  --Bacon.
      [1913 Webster]

   3. Done as if by a machine; uninfluenced by will or emotion;
      proceeding automatically, or by habit, without special
      intention or reflection; as, mechanical singing;
      mechanical verses; mechanical service.
      [1913 Webster]

   4. Made and operated by interaction of forces without a
      directing intelligence; as, a mechanical universe.
      [1913 Webster]

   5. Obtained by trial, by measurements, etc.; approximate;
      empirical. See the 2d Note under Geometric.
      [1913 Webster]

   Mechanical effect, effective power; useful work exerted, as
      by a machine, in a definite time.

   Mechanical engineering. See the Note under Engineering.


   Mechanical maneuvers (Mil.), the application of mechanical
      appliances to the mounting, dismounting, and moving of
      artillery. --Farrow.

   Mechanical philosophy, the principles of mechanics applied
      to the investigation of physical phenomena.

   Mechanical powers, certain simple instruments, such as the
      lever and its modifications (the wheel and axle and the
      pulley), the inclined plane with its modifications (the
      screw and the wedge), which convert a small force acting
      through a great space into a great force acting through a
      small space, or vice versa, and are used separately or in
      combination.

   Mechanical solution (Math.), a solution of a problem by any
      art or contrivance not strictly geometrical, as by means
      of the ruler and compasses, or other instruments.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Engineering \En`gi*neer"ing\, n.
   Originally, the art of managing engines; in its modern and
   extended sense, the art and science by which the properties
   of matter are made useful to man, whether in structures,
   machines, chemical substances, or living organisms; the
   occupation and work of an engineer. In the modern sense, the
   application of mathematics or systematic knowledge beyond the
   routine skills of practise, for the design of any complex
   system which performs useful functions, may be considered as
   engineering, including such abstract tasks as designing
   software (software engineering).
   [1913 Webster +PJC]

   Note: In a comprehensive sense, engineering includes
         architecture as a mechanical art, in distinction from
         architecture as a fine art. It was formerly divided
         into military engineering, which is the art of
         designing and constructing offensive and defensive
         works, and civil engineering, in a broad sense, as
         relating to other kinds of public works, machinery,
         etc.

   Civil engineering, in modern usage, is strictly the art of
      planning, laying out, and constructing fixed public works,
      such as railroads, highways, canals, aqueducts, water
      works, bridges, lighthouses, docks, embankments,
      breakwaters, dams, tunnels, etc.

   Mechanical engineering relates to machinery, such as steam
      engines, machine tools, mill work, etc.

   Mining engineering deals with the excavation and working of
      mines, and the extraction of metals from their ores, etc.
      Engineering is further divided into steam engineering, gas
      engineering, agricultural engineering, topographical
      engineering, electrical engineering, etc.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mechanical engineering
    n 1: the branch of engineering that deals with the design and
         construction and operation of machinery