Etymology: Middle English, from Old English sīde; akin to Old High German sīta side, Old English sīd ample, wide
Date: before 12th century
1 a: the right or left part of the wall or trunk of the body <a pain in the side>b (1): one of the halves of the animal body on either side of the median plane (2): a cut of meat including that about the ribs of one half of the body —used chiefly of smoked pork products c: one longitudinal half of a hide 2: a place, space, or direction with respect to a center or to a line of division (as of an aisle, river, or street) 3 a: one of the longer bounding surfaces or lines of an object especially contrasted with the ends <the side of a barn>b: a line or surface forming a border or face of an object <a die has six sides><the back side of the moon>c: either surface of a thin object <one side of a record><right side of the cloth>d: a bounding line of a geometric figure <side of a triangle> 4 a: the space beside one <stood by my side>b: an area next to something —usually used in combination <a poolside interview> 5: a slope (as of a hill) considered as opposed to another slope <the far side of the hill> 6 a: the attitude or activity of one person or group with respect to another :part<there was no malice on my side>b: a position that is opposite to or contrasted with another <two sides to every question><came down on the side of law and order>c: a body of partisans or contestants <victory for neither side>d:team 4a <11 players on each side>; also: the players on a baseball team batting in an inning <struck out the side> 7: a line of descent traced through one's parent <grandfather on his mother's side> 8: an aspect or part of something contrasted with some other real or implied aspect or part <the better side of his nature><the sales side of the business><the seasoning is a bit on the heavy side> 9British: sideways spin imparted to a billiard or snooker ball 10: a sheet containing the lines and cues for a single theatrical role 11: a recording of music 12: a side order or dish <a side of fries>
— on the side1: in addition to the main portion 2: in addition to a principal occupation 3: secretly outside of one's marriage or romantic relationship <seeing another woman on the side>
— this side of: short of :almost<an attitude just this side of scandalous>