side

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A line bounding a plane figure.
• noun A surface bounding a solid figure.
• noun A surface of an object, especially a surface joining a top and bottom.
• noun A surface of an object that extends more or less perpendicularly from an observer standing in front.
• noun Either of the two surfaces of a thin, flat object.
• noun The part within an object or area to the left or right of the observer or of its vertical axis.
• noun The left or right half of the trunk of a human or animal body.
• noun The space immediately next to someone.
• noun The space immediately next to something. Often used in combination.
• noun One of two or more contrasted parts or places within an area, identified by its location with respect to a center.
• noun An area separated from another area by an intervening feature, such as a line or barrier.
• noun One of two or more opposing individuals, groups, teams, or sets of opinions.
• noun One of the positions maintained in a dispute or debate.
• noun A distinct aspect.
• noun Line of descent.
• noun An incomplete script that shows the lines and cues of a single performer only.
• noun Chiefly British In billiards, the spin given to a propelled ball by striking it off center.
• adjective Located on a side.
• adjective From or to one side; oblique.
• adjective Minor; incidental.
• adjective In addition to the main part; supplementary.
• intransitive verb To provide sides or siding for.
• intransitive verb To be positioned next to.
• intransitive verb To align oneself in a disagreement.
• idiom (on the side) In addition to the main portion.
• idiom (on the side) In addition to the main occupation or activity.
• idiom (side by side) Next to each other; close together.
• idiom (this side of) Verging on; short of.

from The Century Dictionary.

• noun One of the two terminal surfaces, margins, or lines of an object or a space situated laterally to its front or rear aspect; a part lying on the right or the left hand of an observer, with reference to a definite point of view: as, the sides of a building (in contradistinction to its front and rear or back, or to its ends); the sides of a map or of a bed (distinguished from the top and bottom, or from the head and foot, respectively).
• noun Specifically, with reference to an animal body:
• noun Either half of the body, right or left, which lies on either hand of the vertical median longitudinal plane; the entirety of any lateral part or region: as, the right side; the left side.
• noun The whole or a part of the body in front of or behind a vertical transverse plane: as, the front side; the hinder side; the dorsal side.
• noun A part of the body lying laterally with reference to any given or assumed axis, and opposed to another similar or corresponding part: as, the front or back side of the arm.
• noun A surface or extent of any body, or part of any body, that is external or internal, considered with reference to its opposite: as, the inner or outer side. See inside, outside.
• noun Especially, that part of the trunk of an animal which lies or extends between the shoulder and the hip, and particularly the surface of such part; the lateral region or superficies of the chest and belly.
• noun One of the two most extensive surfaces of anything, being neither top or bottom, nor end, nor edge or border.
• noun One of the continuous surfaces of an object limited by terminal lines; one of two or more bounding or investing surfaces; a superficial limit or confine, either external or internal: as, the six sides of a cube (but in geometry the word is not thus used for face, but as synonymous with edge); the side of a hill or mountain (hill side, mountain -side); the upper and under sides of a plank; the right and wrong sides of a fabric or garment (see phrase below); the sides of a cavern or a tunnel.
• noun One of the extended marginal parts or courses of a surface or a plane figure; one of any number of distinct terminal confines or lateral divisions of a surface contiguous to or conterminous with another surface: as, the opposite sides of a road or a river; the east and west sides of the ocean; all sides of a field.
• noun Position or place with reference to an intermediate line or area; a space or stretch divided from another by the limit or course of something: preceded by on and followed by of, either expressed or (sometimes) understood: as, a region on both sides of a river; we shall not meet again this side the grave.
• noun A part of space or a range of thought extending away from a central point; any part of a surrounding region or outlook; lateral view or direction; point of compass: as, there are obstacles on every side; to view a proposition from all sides.
• noun An aspect or part of anything viewed as distinct from or contrasted with another or others; a separate phase; an opposed surface or view (as seen in the compounds inside and outside): as, the side of the moon seen from the earth; a character of many sides; to study all sides of a question; that side of the subject has been fully heard.
• noun Part or position with reference to any line of division or separation; particular standing on a subject; point of view: as, to take the winning side in politics, or one's side of a dispute; there are faults on both sides.
• noun A party or body separated from another in opinion, interest, or action; an opposing section or division; a set of antagonists: as, to choose sides for a game or contest of any kind; different sides in religion or politics.
• noun A divisional line of descent; course of descent through a single ancestor: chiefly with reference to parentage: as, relatives on the paternal or the maternal side; to be well born on the mother's side.