tractrix
noun
trac·trix
ˈtraktriks
plural tractrices
trakˈtrī(ˌ)sēz
: a curve in which the part of the tangent between the point of tangency and a given straight line is constant and which is an involute of a catenary
Word History
Etymology
New Latin, from Latin tractus (past participle of trahere to draw) + -trix