What is "diminishing rule"

Diminish \Di*min"ish\, v. t. [imp. & p. p. Diminished; p. pr. & vb. n. Diminishing.] [Pref. di- (= L. dis-) + minish: cf. L. diminuere, F. diminuer, OE. diminuen. See Dis-, and Minish.]

1. To make smaller in any manner; to reduce in bulk or amount; to lessen; -- opposed to augment or increase.

   Not diminish, but rather increase, the debt.
   --Barrow.

2. To lessen the authority or dignity of; to put down; to degrade; to abase; to weaken.

   This doth nothing diminish their opinion.
   --Robynson (More's Utopia).

   I will diminish them, that they shall no more rule over the nations.
   --Ezek. xxix. 15.

   O thou . . . at whose sight all the stars Hide their diminished heads.
   --Milton.

3. (Mus.) To make smaller by a half step; to make (an interval) less than minor; as, a diminished seventh.

4. To take away; to subtract.

   Neither shall ye diminish aught from it.
   --Deut. iv. 2.

   Diminished column, one whose upper diameter is less than the lower.

   Diminished scale, or Diminishing scale, a scale of gradation used in finding the different points for drawing the spiral curve of the volute.
   --Gwilt.

   Diminishing rule (Arch.), a board cut with a concave edge, for fixing the entasis and curvature of a shaft.

   Diminishing stile (Arch.), a stile which is narrower in one part than in another, as in many glazed doors.

   Syn: To decrease; lessen; abate; reduce; contract; curtail; impair; degrade. See Decrease.