The general definition of a grandfather clock or floor clock is that it is free-standing, and therefore not a wall clock, or hung on a wall like wall clocks. Having said that, many individuals refer to their wall clocks as grandfather wall clocks. We think sometimes people do this because there wall clocks are large and have many of the characteristics of grandfather clocks, e.g. cable driven or chain driven, a moonphase dial, weights, a pendulum and more.
Having said that, the very definition of a discount floor clock or grandfather clock is that it stands by itself, so there is really no easily mistaking a grandfather clock for a wall clock.
We have yet to have any customer refer to a grandfather mantle clock, or a grandmother mantel clock, but we have had people refer to their mantle clocks or mantel clocks as being like grandfather clocks when they are on a decorative shelf, particularly if the clock is tall and has many of the same clocks features as described above.
Anyone care to invent grandfather alarm clocks that will REALLY wake you up?