The Collaborative International Dictionary of English v.0.48:

Lateral \Lat"er*al\, a. [L. lateralis, fr. latus, lateris, side:
   cf. F. lat['e]ral.]
   1. Of or pertaining to the sides; as, the lateral walls of a
      house; the lateral branches of a tree.
      [1913 Webster]

   2. (Anat.) Lying at, or extending toward, the side; away from
      the mesial plane; external; -- opposed to mesial.
      [1913 Webster]

   3. Directed to the side; as, a lateral view of a thing.
      [1913 Webster]

   Lateral cleavage (Crystallog.), cleavage parallel to the
      lateral planes.

   Lateral equation (Math.), an equation of the first degree.
      [Obs.]

   Lateral line (Anat.), in fishes, a line of sensory organs
      along either side of the body, often marked by a distinct
      line of color.

   Lateral pressure or stress (Mech.), a pressure or stress
      at right angles to the length, as of a beam or bridge; --
      distinguished from longitudinal pressure or stress.

   Lateral strength (Mech.), strength which resists a tendency
      to fracture arising from lateral pressure.

   Lateral system (Bridge Building), the system of horizontal
      braces (as between two vertical trusses) by which lateral
      stiffness is secured.
      [1913 Webster] lateral

WordNet (r) 3.0 (2006):

lateral line
    n 1: sense organs of fish and amphibians; believed to detect
         pressure changes in the water [syn: lateral line,
         lateral line organ]