LITUUS

Etymology

Noun

lituus (plural litui)

A military trumpet.

(geometry) A curve with polar equation $$r^2 \theta = a^2$$ , where a is a constant.

Source: Wiktionary

Lit"u*us, n.; pl. Litui. Etym: [L.]

1. (Rom. Antig.) (a) A curved staff used by the augurs in quartering the heavens. (b) An instrument of martial music; a kind of trumpet of a somewhat curved form and shrill note.

2. (Math.)

Definition: A spiral whose polar equation is r2th = a; that is, a curve the square of whose radius vector varies inversely as the angle which the radius vector makes with a given line.

Source: Webster’s Unabridged Dictionary 1913 Edition