%retard%

adj. able to reduce combustibility or slow the spread of fire; -- of substances that are added to combustible materials to make them less combustible.
PJC ]

v. t. [ imp. & p. p. Retarded; p. pr. & vb. n. Retarding. ] [ L. retardare, retardatum; pref. re- re- + tardare to make slow, to delay, fr. tardus slow: cf. F. retarder. See Tardy. ] 1. To keep delaying; to continue to hinder; to prevent from progress; to render more slow in progress; to impede; to hinder; as, to retard the march of an army; to retard the motion of a ship; -- opposed to accelerate. [ 1913 Webster ]

2. To put off; to postpone; as, to retard the attacks of old age; to retard a rupture between nations. [ 1913 Webster ]

Syn. -- To impede; hinder; obstruct; detain; delay; procrastinate; postpone; defer. [ 1913 Webster ]

v. i. To stay back. [ Obs. ] Sir. T. Browne. [ 1913 Webster ]

n. 1. Retardation; delay. [ 1913 Webster ]

2. A mentally retarded person. [ Colloq. and disparaging ] [ PJC ]

3. a person who is stupid or inept, especially in social situations. [ Colloq. and disparaging ] [ PJC ]

Retard of the tide, or
Age of the tide, the interval between the transit of the moon at which a tide originates and the appearance of the tide itself. It is found, in general, that any particular tide is not principally due to the moon's transit immediately proceeding, but to a transit which has occured some time before, and which is said to correspond to it. The retard of the tide is thus distinguished from the lunitidal interval. See under Retardation. Ham. Nav. Encyc. [ 1913 Webster ]

n. [ L. retardatio: cf. F. retardation. ] 1. The act of retarding; hindrance; the act of delaying; as, the retardation of the motion of a ship; -- opposed to acceleration. [ 1913 Webster ]

The retardations of our fluent motion. De Quinsey. [ 1913 Webster ]

2. That which retards; an obstacle; an obstruction. [ 1913 Webster ]

Hills, sloughs, and other terrestrial retardations. Sir W. Scott. [ 1913 Webster ]

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. [ 1913 Webster ]

4. The extent to which anything is retarded; the amount of retarding or delay. [ 1913 Webster ]

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. [ 1913 Webster ]

a. [ Cf. F. retardatif. ] Tending, or serving, to retard. [ 1913 Webster ]

n. having a limited or below normal mental ability; same as
mentally retarded; -- used especially in relation to performance in academic tasks. [ PJC ]

n. 1. One who, or that which, retards. [ 1913 Webster ]

2. (Steam Boiler) Any of various devices, as a helix of flat metal strip, introduced into a boiler tube to increase the heating effect of the fire. [ Webster 1913 Suppl. ]

3. (Photog.) A substance, as potassium bromide, added to a developer to retard its action. [ Webster 1913 Suppl. ]