\De`vi*a"tion\, n. [LL. deviatio: cf. F.
d['e]viation.]
1. The act of deviating; a wandering from the way; variation
   from the common way, from an established rule, etc.;
   departure, as from the right course or the path of duty.
2. The state or result of having deviated; a transgression;
   an act of sin; an error; an offense.
2. (Com.) The voluntary and unnecessary departure of a ship
   from, or delay in, the regular and usual course of the
   specific voyage insured, thus releasing the underwriters
   from their responsibility.
{Deviation of a falling body} (Physics), that deviation from
   a strictly vertical line of descent which occurs in a body
   falling freely, in consequence of the rotation of the
   earth.
{Deviation of the compass}, the angle which the needle of a
   ship's compass makes with the magnetic meridian by reason
   of the magnetism of the iron parts of the ship.
{Deviation of the line of the vertical}, the difference
   between the actual direction of a plumb line and the
   direction it would have if the earth were a perfect
   ellipsoid and homogeneous, -- caused by the attraction of
   a mountain, or irregularities in the earth's density.