Retardation

n.	1.	The act of retarding; hindrance; the act of delaying; as, the retardation of the motion of a ship; - opposed to acceleration. The retardations of our fluent motion. - De Quinsey.
	2.	That which retards; an obstacle; an obstruction. Hills, sloughs, and other terrestrial retardations. - Sir W. Scott.
	3.	(Mus.) The keeping back of an approaching consonant chord by prolonging one or more tones of a previous chord into the intermediate chord which follows; - differing from suspension by resolving upwards instead of downwards.
	4.	The extent to which anything is retarded; the amount of retarding or delay. Retardation of the tide a - The lunitidal interval, or the hour angle of the moon at the time of high tide any port; the interval between the transit of the moon and the time of high tide next following b - The age of the tide; the retard of the tide. See under Retard, n.

Noun	1.	retardation - a decrease in speed; "the deceleration of the arms race" Synonyms: deceleration, slowing
	2.	retardation - the extent to which something is delayed or held back
	3.	retardation - any agent that retards or delays or hinders; "flame-retardant" Synonyms: retardant, retardent
	4.	retardation - lack of normal development of intellectual capacities Synonyms: backwardness, mental retardation, subnormality, slowness
	5.	retardation - the act of slowing down or falling behind Synonyms: lag, slowdown

afterthought, amentia, arrest, arrestation, arrested development, arrestment, backwardness, bind, blithering idiocy, block, blockage, blocking, bureaucratic delay, check, clogging, closing up, closure, constraint, constriction, control, cooling, cooling down, cooling off, cramp, cretinism, curb, curtailment, deceleration, delay, delayage, delayed reaction, detainment, drag, dragging, ease-off, ease-up, fixation, flagging, foot-dragging, half-wittedness, halt, hampering, hang-up, hindering, hindrance, holdback, holdup, idiocy, idiotism, imbecility, impediment, infantilism, inhibition, injunction, insanity, interdict, interference, interim, interruption, jam, lag, lagging, legal restraint, let, letdown, letup, logjam, mental defectiveness, mental deficiency, mental handicap, mental retardation, minus acceleration, mongolianism, mongolism, mongoloid idiocy, monopoly, moratorium, moronism, moronity, negativism, nuisance value, obstruction, obstructionism, occlusion, opposition, paperasserie, pause, profound idiocy, prohibition, protection, protectionism, protective tariff, rationing, red tape, red-tapeism, red-tapery, rein, repression, reprieve, resistance, respite, restraint, restraint of trade, restriction, retardance, retardment, retrenchment, self-control, setback, simple-wittedness, simplemindedness, simpleness, simplicity, slack-up, slackening, slow-up, slowdown, slowing, slowing down, slowness, slowup, squeeze, stay, stay of execution, stop, stoppage, stranglehold, stricture, subnormality, suppression, suspension, tariff wall, thought control, tie-up, time lag, wait