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The Collaborative International Dictionary of English v.0.48 (gcide)

Friction \Fric"tion\, n. [L. frictio, fr. fricare, frictum,to
rub: cf. F. friction. See {Fray} to rub, arid cf.
{Dentifrice}.]
1. The act of rubbing the surface of one body against that of
another; attrition; in hygiene, the act of rubbing the
body with the hand, with flannel, or with a brush etc., to
excite the skin to healthy action.
[1913 Webster]

2. (Mech.) The resistance which a body meets with from the
surface on which it moves. It may be resistance to sliding
motion, or to rolling motion.
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3. A clashing between two persons or parties in opinions or
work; a disagreement tending to prevent or retard
progress.
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{Angle of friction} (Mech.), the angle which a plane onwhich
a body is lying makes with a horizontal plane,when the
hody is just ready to slide dewn the plane.

Note: This angle varies for different bodies, and for planes
of different materials.

{Anti-friction wheels} (Mach.), wheels turning freely on
small pivots, and sustaining, at the angle formed by their
circumferences, the pivot or journal of a revolving shaft,
to relieve it of friction; -- called also {friction
wheels}.

{Friction balls}, or

{Friction rollers}, balls or rollers placed so as to receive
the pressure or weight of bodies in motion, and relieve
friction, as in the hub of a bicycle wheel.

{Friction brake} (Mach.), a form of dynamometer for measuring
the power a motor exerts. A clamp around the revolving
shaft or fly wheel of the motor resists the motion by its
friction, the work thus absorbed being ascertained by
observing the force required to keep the clamp from
revolving with the shaft; a Prony brake.

{Friction chocks}, brakes attached to the common standing
garrison carriages of guns, so as to raise the trucks or
wheels off the platform when the gun begins to recoil, and
prevent its running back. --Earrow.

{Friction clutch}, {Friction coupling}, an engaging and
disengaging gear for revolving shafts, pulleys, etc.,
acting by friction; esp.:
(a) A device in which a piece on one shaft or pulley is so
forcibly pressed against a piece on another shaft that
the two will revolve together; as, in the
illustration, the cone a on one shaft, when thrust
forcibly into the corresponding hollow cone b on the
other shaft, compels the shafts to rotate together, by
the hold the friction of the conical surfaces gives.
(b) A toothed clutch, one member of which, instead of
being made fast on its shaft, is held by friction and
can turn, by slipping, under excessive strain or in
starting.

{Friction drop hammer}, one in which the hammer is raised for
striking by the friction of revolving rollers which nip
the hammer rod.

{Friction gear}. See {Frictional gearing}, under
{Frictional}.

{Friction machine}, an electrical machine, generating
electricity by friction.

{Friction meter}, an instrument for measuring friction, as in
testing lubricants.

{Friction powder}, {Friction composition}, a composition of
chlorate of potassium, antimony, sulphide, etc, which
readily ignites by friction.

{Friction primer}, {Friction tube}, a tube used for firing
cannon by means of the friction of a roughened wire in the
friction powder or composition with which the tube is
filled.

{Friction wheel} (Mach.), one of the wheels in frictional
gearing. See under {Frictional}.
[1913 Webster]